It is possible to obtain an engine starting device in which, at the time of initial engagement of a first pinion gear and an engine starting gear, in a case where the first pinion gear collides with the engine starting gear, the first pinion gear is inclined with respect to the second pinion gear, a void having a predetermined size for expanding the inclined state is formed between a surface of an end surface portion of the first pinion gear on the side of an end surface portion of the second pinion gear, and a surface of an end surface portion of the second pinion gear on the side of the end surface portion of the first pinion gear, even in a case where any one of the rotation speed of the engine starting gear and the rotation speed of the pinion gear is larger than the other, rotation synchronization of the engine starting gear and the pinion gear and phase focusing of the teeth between the engine starting gear and the pinion gear is further rapidly and further reliably performed at the time when the engine starting gear and the pinion gear is abutted to each other, noise is decreased, and shortening of the life due to abrasion can be suppressed.