A body insertable apparatus comprising: a function executing unit configured to execute a predetermined function in a body into which the body insertable apparatus is inserted; an electric-power accumulating unit configured to accumulate electric power for driving the function executing unit; an exhaustion unit provided separately from the function executing unit and configured to exhaust the electric power in the electric-power accumulating unit; a switching controller provided between the electric-power accumulating unit and the function executing unit and configured to selectively supply electric power from the electric-power accumulating unit to the function executing unit; a protection circuit configured to control the switching controller and to detect a voltage at a point between the switching controller and the function executing unit; a field effect transistor provided between the electric-power accumulating unit and the exhaustion unit and configured to selectively supply electric power from the electric-power accumulating unit to the exhaustion unit; a voltage detecting circuit configured to control the field effect transistor and to detect a voltage at a point between the electric-power accumulating unit and the exhaustion unit, wherein when the voltage detected by the voltage detecting circuit is not smaller than a second threshold voltage that is higher than a first threshold voltage, the electric power from the electric-power accumulating unit is exclusively supplied to the function executing unit, when the voltage detected by the voltage detecting circuit becomes smaller than the second threshold voltage, the electric power from the electric-power accumulating unit is at the same time supplied to the function executing unit and the exhaustion unit and a resistance value of the exhaustion unit is reduced, and when the voltage detected by the protection circuit becomes smaller than the first threshold voltage, the electric power from the electric-power accumulating unit is exclusively supplied to the exhaustion unit. a function executing unit configured to execute a predetermined function in a body into which the body insertable apparatus is inserted; an electric-power accumulating unit configured to accumulate electric power for driving the function executing unit; an exhaustion unit provided separately from the function executing unit and configured to exhaust the electric power in the electric-power accumulating unit; a switching controller provided between the electric-power accumulating unit and the function executing unit and configured to selectively supply electric power from the electric-power accumulating unit to the function executing unit; a protection circuit configured to control the switching controller and to detect a voltage at a point between the switching controller and the function executing unit; a field effect transistor provided between the electric-power accumulating unit and the exhaustion unit and configured to selectively supply electric power from the electric-power accumulating unit to the exhaustion unit; a voltage detecting circuit configured to control the field effect transistor and to detect a voltage at a point between the electric-power accumulating unit and the exhaustion unit, wherein when the voltage detected by the voltage detecting circuit is not smaller than a second threshold voltage that is higher than a first threshold voltage, the electric power from the electric-power accumulating unit is exclusively supplied to the function executing unit, when the voltage detected by the voltage detecting circuit becomes smaller than the second threshold voltage, the electric power from the electric-power accumulating unit is at the same time supplied to the function executing unit and the exhaustion unit and a resistance value of the exhaustion unit is reduced, and when the voltage detected by the protection circuit becomes smaller than the first threshold voltage, the electric power from the electric-power accumulating unit is exclusively supplied to the exhaustion unit.