Seatbelt apparatus includes a control device connected with a vehicle-mounted battery for controlling an operational state of a seatbelt on the basis of an opened/closed state of a buckle switch and electric power supplied by the battery. The control device has a first operation mode for operating with low-level electric power, and a second operation mode for operating with higher-level electric power. In the second operation mode, the control device is kept in a state capable of detecting the opened/closed state of the buckle switch. The apparatus also includes a storage section for storing a current state value of the buckle switch when the control device shifts from the second operation mode to the first operation mode.