An internal short-circuit detecting device for detecting an internal short circuit of a battery being subjected to constant current charge using a constant current amount (I) has: a voltage detection unit for detecting a terminal voltage of the battery; a terminal voltage acquisition unit for acquiring a terminal voltage (V1), as predetermined by the voltage detection unit, at a starting point of a first period (ΔW1) and a terminal voltage (V2) at an ending point; a voltage increase amount calculation unit for calculating an actual increase amount (ΔV3) of the terminal voltage of the first period (ΔW1) from the terminal voltages (V1 and V2); a voltage increase amount prediction unit for calculating a predicted increase amount (ΔV4) of the terminal voltage for the period when charging is performed using the current amount (I) for the first period (ΔW1); and an internal short-circuit determination unit for determining that the internal short circuit is generated when the actual increase amount (ΔV3) is equal to or lower than the sum of the predicted increase amount (ΔV4) and a predetermined coefficient (α).