An accelerator device includes a first cover that provides an internal space for housing a return spring and a failure region where the first cover engages a second cover. The failure region has a thickness configured to be thinner than a thickness of a body of the first cover. When a pedal rotates to open an accelerator, a second cover side friction member creates a force that pushes the second cover toward an outside of the device. The force is relayed to a contact portion of the first cover via a contact portion of the second cover and causes a failure of the failure region. As a result, the return spring is prevented from falling out of the internal space when the body breaks.