To provide a member fixing structure which can maintain fixing durability and accuracy between a gear member and a shaft member.

The member fixing structure fixes a gear member 1 and a shaft member 3, and includes: an press-fitting part 5 including an outer peripheral press-fitting surface 13 disposed in the shaft member 3 and an inner peripheral press-fitting surface 15 disposed in the gear member 1 and press-fitted into the outer peripheral press-fitting surface 13; a joint part 7 where a shaft side joint surface 37 and a gear side joint surface 25 abut on each other in an axial direction and welded and coupled together at a place different from the press-fitting part 5; a gap part 9 formed between the gear member 1 side and the shaft member 3 side between the press-fitting part 5 and the joint part 7; and a communication path 11 which is disposed at the flange part 33 of the shaft member 3 and opens the gap part 9 to the outside between the press-fitting part 5 and the joint part 7.