A planetary gear device includes: a first internal gear and a second internal gear, a first external gear which meshes with the first internal gear, a second external gear which meshes with the second internal gear, and an eccentric body which circumferentially moves the first external gear and the second external gear. The first external gear and the second external gear each independently have external teeth and are connected to each other to integrally rotate with each other, the first internal gear and the second internal gear each independently have internal teeth, one of the first internal gear and the second internal gear is connected to a stationary side, and the other thereof is connected to an output side, and each of the first internal gear and the second internal gear has internal teeth which are constituted by a support body, and a rotating body rotatable to the support body.