A battery load power detecting system includes a generator current sensor which detects a current supplied from a generator to at least one of a battery and a load group including a steering device, and first and second load current sensors which detect a current supplied from at least one of the generator and the battery to the load group. A battery state monitor calculates a load power of the battery by multiplying a difference between both the currents by a voltage at a terminal of the battery detected by a voltage sensor. Therefore, the load state of the battery can be appropriately confirmed to avoid a situation where the steering device, e.g., a steering-by-wire type steering device, falls into an inoperable state due to power deficiency.