A yo-yo includes a pair of rotary elements spaced from each other and each having a cavity, a bearing portion formed on each of the pair of rotary elements at a center thereof, and an axle detachably received in the bearing portion so as to be rotatable together with the pair of rotary elements. The axle has an engaging portion formed at each of opposite ends thereof. The axle is loosely inserted into a generally cylindrical spool interposed between the pair of rotary elements. A locking device having a pair of locking parts is mounted in the cavity, and the pair of locking parts have respective holding portions for detachably holding the engaging portion therebetween.