The announcement Wednesday makes Pridemore the 12th Republican and 18th Assembly member overall to decide against seeking re-election.
The conservative Pridemore ran for state superintendent of schools in 2013 but lost to incumbent Tony Evers.
Pridemore, of Erin, has been in the Assembly for 10 years. The 67-year-old says in his retirement announcement that he never believed elected office should be a long career and now is the time to step aside.
Pridemore's district covers portions of Washington, Waukesha and Milwaukee counties.
He is one of 60 Republicans in the Assembly. There are 39 Democrats.