Exercise aiding apparatus includes a step 2 that a user puts a user's foot on, and a step drive means 5 that causes the step to perform movement including turning motion so that exercise is performed with respect to the foot put on the step. The apparatus includes a lock means 6 that fixes the step by engagement with the step except when the step drive means 5 drives the step. When the step is not driven, the step is fixed. The step is prevented from moving inadvertently at getting on and off, thereby ensuring safe getting on and off.