The twice champions were far too good for their African neighbours at the North Harbour Stadium with winger Bryan Habana registering the try he needed to become the Springboks' record try scorer.
The result leaves South Africa a victory away from winning Pool D and setting up a likely quarter-final against Tri-Nations champions Australia.
Although the win was never in doubt and the winning margin the biggest in the tournament so far, the 10 first-half handling errors would concerned South African coach Peter de Villiers.
"Our first 40 we got sucked into a few bad habits. Probably a bit too loose too early," Springbok captain John Smit said in a pitchside interview.
"At half time we refocused and stuck to our guns and got into a bit more shape and got a bit more reward in the second half. It was a good run out."
Recalled winger Gio Aplon scored the opening try in the seventh minute after a neat interception by Smit before Habana raced in for the second 15 minutes later from 40 metres after a teasing flat pass by lock Danie Rossouw.
The try meant Habana ended a 15-month drought and moved him ahead of former scrumhalf Joost van der Westhuizen onto 39 in the Springbok records list.
De Villiers had opted to go with a number of first-choice players in his lineup despite the inferior opposition and, in the pack especially, the experience told.
Numerous scrum penalties conceded by Namibia near their line resulted in referee George Clancy of Ireland awarding a penalty try on the half hour.
The Springboks claimed the four-try bonus point seven minutes later when centre Jaque Fourie collected a neat offload by Frans Steyn in the tackle to run in under the posts.
Namibia have never won a World Cup game and barring a couple of bright linebreaks by flanker Tinus Du Plessis and their quick winger Heine Bock they never threatened as the Springboks went in 31-0 up at halftime.
More tries followed in the second half as the Springboks became more clinical with inside centre Frans Steyn finishing off after a neat pass from number eight Pier Spies.
However, there was a scare for the Springboks when lock Bakkies Botha winced off after the try having been slow to get to his feet after a cutting tackle below the knee in the move that led to the score.
Flyhalf Morne Steyn was again impressive with the boot, not missing a kick as he contributed 20 points after converting his own try from the touchline on the hour before exiting to the replacement bench.
"Very disappointing," said Namibia captain Jacques Burger.
"We said coming in that we had to keep the mistakes down to a minimum and we just made too many mistakes and a good side like the Boks will cut you apart and that's what they did."