A lamp holding apparatus for mounting a lamp to a base member includes a mounting plate having a pair of locking portions protruding to a base side. The locking portion is inserted into a mounting hole provided at the base and capable of being locked to a peripheral edge on its back side. Abutting portions, which protrude to the base side and are capable of abutting the base at the time of mounting, are provided on a bottom surface of the mounting plate that is an opposing surface to the base. The abutting portions are provided at three spots with one of the locking portions interposed therebetween. At the time of mounting, each of the abutting portions abut the base, and the mounting plate is elastically deformed so as to be warped, whereby the locking surface of the locking portion is kept in the state in which it is locked to a peripheral edge of a back side of the mounting hole by its elastic force.