An injection molding machine comprising a mold falling prevention device that prevents a mold attached to a mold fixing surface (11a, 12a) from falling off from the mold fixing surface, the injection molding machine comprising: a bottom edge restriction member that is provided to a lower portion of the mold fixing surface so that its position in a vertical direction is variable, for implementing restriction so that a bottom edge portion of the mold does not separate from the mold fixing surface; and first and second intermediate restriction members that are provided to intermediate level portions of the mold fixing surface so that their positions in a horizontal direction are variable, for respectively implementing restrictions so that a one edge portion of the mold and an other edge portion thereof in the horizontal direction do not separate from the mold fixing surface; wherein a vertical direction position determination mechanism that receives and stops a bottom edge surface of the mold and determines a position of the mold in the vertical direction is provided at a lower portion of the mold fixing surface; said vertical direction position determination mechanism comprises a base member fixed to the mold fixing surface, a bottom edge mold reception member disposed above the base member, a pair of guide rods that guide said bottom edge mold reception member so that it is capable of ascending and descending with respect to the base member, a fluid pressure cylinder provided to the base member and capable of raising and lowering said bottom edge mold reception member, and a plurality of support members installed between the base member and said bottom edge mold reception member and capable of supporting the mold; and said bottom edge mold reception member and said bottom edge restriction member are formed integrally with one another. a bottom edge restriction member that is provided to a lower portion of the mold fixing surface so that its position in a vertical direction is variable, for implementing restriction so that a bottom edge portion of the mold does not separate from the mold fixing surface; and first and second intermediate restriction members that are provided to intermediate level portions of the mold fixing surface so that their positions in a horizontal direction are variable, for respectively implementing restrictions so that a one edge portion of the mold and an other edge portion thereof in the horizontal direction do not separate from the mold fixing surface; wherein a vertical direction position determination mechanism that receives and stops a bottom edge surface of the mold and determines a position of the mold in the vertical direction is provided at a lower portion of the mold fixing surface; said vertical direction position determination mechanism comprises a base member fixed to the mold fixing surface, a bottom edge mold reception member disposed above the base member, a pair of guide rods that guide said bottom edge mold reception member so that it is capable of ascending and descending with respect to the base member, a fluid pressure cylinder provided to the base member and capable of raising and lowering said bottom edge mold reception member, and a plurality of support members installed between the base member and said bottom edge mold reception member and capable of supporting the mold; and said bottom edge mold reception member and said bottom edge restriction member are formed integrally with one another.