To provide an internal gear pump which is able to stably ensure the sealing property between a resin casing constituting a trochoid accommodating portion and a cover, to omit the seal ring at the portion, and to stabilize the discharging ability. An internal gear pump 1 has a trochoid 4 in which an inner rotor 3 having a plurality of outer teeth is accommodated in an outer rotor 2 having a plurality of inner teeth in a state in which outer teeth mesh with inner teeth and are eccentric, and a casing 5 having a trochoid accommodating recess 5a formed therein, and a cover 6 which closes the recess 5a. The casing 5 is an injection-molded body of a resin composition. The casing 5 and the cover 6 are fixed with bolts. A metallic bush 7 is provided in the bolt fixing hole portion of the casing 5. In the cross-section of the joining portion between the casing 5 and the cover 6, the position of the end surface 7a of the bush 7 is higher than the bush formation surface 5e around the bush of the casing 5 and lower than the sealing surface 5d around the recess of the casing 5, as viewed from the bottom surface 5c of the recess 5a.