A disk friction clutch apparatus using a self-energizing effect is disclosed. The clutch apparatus includes a drive friction disk connected to a drive shaft, a driven friction disk connected to a driven shaft, a push member configured to press the driven friction disk against the drive friction disk at an engagement position of a clutch, and an operation unit configured to shift the push member from the release position of the clutch to the engagement position. The operation unit is operated to increase a force of the push member to press the driven friction disk when the push member located at the engagement position of the clutch receives a force of rotating the drive shaft. Since the clutch apparatus employs a self-energizing effect, it is possible to fasten the clutch with a small force.