France scored two tries through prop Rabah Slimani and replacement forward Nicolas Mas to one for Italy wing Giovanbattista Venditti.
The French might have had a try in the first half but were denied for a knock-on which it took referee Craig Joubert two consultations with the TMO to resolve.
France, 15-3 up at the interval after a first half dominated by penalties mainly given away by the Italians with Michalak punishing four and fullback Scott Spedding one from inside the French half, hit the second half running.
Michalak converted his fifth penalty before a series of quick-passing attacks led to the first try after 44 minutes.
Spedding took a high ball deep in French territory and launched a counter-attack that had Noa Nakaitaci feeding hooker Guilhem Guirado who was stopped short at the base of the post.
Then from a ruck close to the Italy line, Michalak breached the defence with a neat grubber which Slimani chased to touch down under the posts.
Italy hit back with a series of attacks on the French line, a messy try disallowed for knock-on before Venditti ran over on the right to score with Tomasso Allan converting.
Ten minutes into the match, number eight Louis Picamoles made a break down the right and fed Nakaitaci before the line with a pass that hit another player on the way and the wing went down to score what appeared to be a try.
South African Joubert consulted the TMO because he wanted to be sure the ball had come off an Italian to Nakaitaci and then gave the try.
However, alerted by Italian jeering in the crowd and seeing on the stadium screen that the wing’s touchdown was not clean, he went back to the TMO, who confirmed the knock-on, and Joubert reversed his decision.
Instead he gave a penalty, one of seven Michalak kicked in the match, converting five with the other two coming back off the posts as he edged to within three points of Thierry Lacroix’s French World Cup points record of 124.
(Reporting by Toby Davis/Rex Gowar; editing by Justin Palmer)