The 24-year-old attacker agreed a four-deal at Upton Park with a two-year option. No transfer fee was disclosed.
Maiga is the newly promoted Premier League club's fifth close-season arrival, following Mohamed Diame, George McCartney, Jussi Jaaskelainen and Stephen Henderson.
"I know West Ham are a big club in England and I'm really looking forward to representing them," Maiga told West Ham's website (www.whufc.com).
"They have huge tradition and it is like joining part of a family and that is one of the main reasons I wanted to come here."
In two seasons with FC Sochaux, Maiga played in 59 Ligue 1 matches and scored 24 goals.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO Sports and on Facebook at AhramOnlineSports)