An internal gear pump comprising: an inner gear that has plural outer teeth (T11 to T17) on an outer peripheral surface of the inner gear; and an outer gear that is formed with a housing space that is capable of housing the inner gear and includes plural inner teeth (T21 to T28) that mesh with the outer teeth (T11 to T17) on an inner peripheral surface that forms the housing space, one of the inner teeth and the outer teeth having a shape based on a tooth shape that is respectively formed from a generating curve of the other of the inner teeth and the outer teeth, the internal gear pump characterised by a section of each of the inner teeth that protrudes in a direction toward the inner gear having a first arc shape (Cro), a section of each of the outer teeth that protrudes in a direction toward the outer gear having a curved shape, each of both end sections of the curved shape having a second arc shape (Cri), if a radius of the first arc shape (Cro) is set as ro, a radius of the second arc shape (Cri) is set as ri, a diameter of a pitch circle of the inner teeth is set as dp, and the number of the inner teeth of the outer gear is set as z, the inner gear and the outer gear each having a shape that satisfies a relationship established by following equations: 1.6 > ro/(dp/z) > 1.0; and ro/(dp/z) > ri/(dp/z) ≥ 0.13, and each of the inner teeth being provided so that an intersecting point that is between one (Cro) of arcs that follow the first arc shapes of the adjacent inner teeth and the pitch circle (Co) of the inner teeth and that is in proximity to the other arc (Cro) is located outside of the other arc (Cro). an inner gear that has plural outer teeth (T11 to T17) on an outer peripheral surface of the inner gear; and an outer gear that is formed with a housing space that is capable of housing the inner gear and includes plural inner teeth (T21 to T28) that mesh with the outer teeth (T11 to T17) on an inner peripheral surface that forms the housing space, one of the inner teeth and the outer teeth having a shape based on a tooth shape that is respectively formed from a generating curve of the other of the inner teeth and the outer teeth, the internal gear pump characterised by a section of each of the inner teeth that protrudes in a direction toward the inner gear having a first arc shape (Cro), a section of each of the outer teeth that protrudes in a direction toward the outer gear having a curved shape, each of both end sections of the curved shape having a second arc shape (Cri), if a radius of the first arc shape (Cro) is set as ro, a radius of the second arc shape (Cri) is set as ri, a diameter of a pitch circle of the inner teeth is set as dp, and the number of the inner teeth of the outer gear is set as z, the inner gear and the outer gear each having a shape that satisfies a relationship established by following equations: 1.6 > ro/(dp/z) > 1.0; and ro/(dp/z) > ri/(dp/z) ≥ 0.13, and each of the inner teeth being provided so that an intersecting point that is between one (Cro) of arcs that follow the first arc shapes of the adjacent inner teeth and the pitch circle (Co) of the inner teeth and that is in proximity to the other arc (Cro) is located outside of the other arc (Cro).