An interposer assembly having a housing with contact positioning holes each having a first wall face and a second wall face. The interposer contact has a base portion with shoulder portions and contact arm portions. The base portion is closer to the first wall face. The contact arm portions are once bulged from both respective vertical ends of the base portion toward the first wall face and then curved toward the second wall face. The housing has a retaining protrusion and a pair of slit portions. The retaining protrusion retains the interposer contact inside the contact positioning hole. Each of the shoulder portions is inserted into the slit portion. The slit portion blocks the interposer contact from moving toward the second wall face.