A member junction structure includes a first member provided with a first press-fitting portion and a second press-fitting portion, and a second member provided with a first press-fitted portion and a second press-fitted portion and configured to be installed on the first member by moving in a first direction which is a predetermined one direction with respect to the first member. In a state where the second member is halfway to be installed on the first member, the first press-fitting portion is inserted into the second press-fitted portion, thereby providing a guide for installing the second member on the first member. In a state where the second member is completely installed on the first member, the first press-fitting portion is press-fitted into the first press-fitted portion, and the second press-fitting portion is press-fitted into the second press-fitted portion.