To provide an injection molded shaft that can absorb a shock caused by sudden changes in torque by undergoing twisting deformation of a shaft body when sudden changes in torque are applied. [Solution] In a shaft body 2, one end in an axial direction of a core part 18 having a crisscross cross section orthogonal to the axial direction is connected to a helical gear 3 via a first connecting part 15 and the other end in the axial direction of the core part 18 is connected to a worm 4 via a second connecting part 16. A plurality of first framework parts 21 are formed at regular intervals along a direction of a shaft core in the core part 18 between the first connecting part 15 and the second connecting part 16. A second framework part 22 extends across the first connecting part 15, the first framework part 21, and the core part 18 like a diagonal brace. A third framework part 23 extends across a pair of the first framework parts 21 and 21 adjacent to each other and the core part 18 like a diagonal brace. A fourth framework part 24 extends across the second connecting part 16, the first framework part 21, and the core part 18 like a diagonal brace.