A MIG welded joint between aluminum and steel members is obtained by overlapping the aluminum member and the steel member each other and performing MIG welding using a filler wire made of a 4000 or 5000 series aluminum alloy on an end face of the overlapped aluminum member, wherein the aluminum member has a thickness P ranging from 0.5 to 2.0 mm, and the steel member has a thickness Q satisfying the following formula: 0.6≦Q/P≦0.8, whereby a penetration depth of the steel member is equal to or less than 5% of the thickness Q thereof.