A clutch including a drive shaft, drive side rotation body, driven shaft, driven side rotation body, clutch housing, and lock member is disclosed. During non-rotation of the drive side rotation body, when the driven side rotation body is rotated, the lock member is pushed by the driven side rotation body and moved outward in a radial direction thereby bringing the contact portion into contact with the inner circumferential surface of the clutch housing. During rotation of the drive side rotation body, the drive side rotation body pushes a drive side cam surface in the rotation direction, and the drive side cam surface acts to move the lock member inward in the radial direction and push the lock member against the driven side rotation body. Thus, the lock member is sandwiched between the drive side rotation body and the driven side rotation body thereby coupling the drive side rotation body and the driven side rotation body with the lock member to be integrally rotatable.