A toner replenishment device includes a toner receiving port, a toner feed unit feeding toner from the toner receiving port into the device, a toner detector detecting that the device has been filled with a specified amount of the toner, an agitating member having an agitating blade and rotating so as to agitate the toner in the device, a position detector detecting a rotational position of the agitating member and generating a signal indicative thereof, and a recognition unit recognizing the rotational position based on the signal output from the position detector. The toner feed unit feeds the toner into the device when an end edge of the agitating blade is within a specified range, in which a flow path of the toner from the toner receiving port to the toner detector is not blocked by the agitating blade, based on the recognition performed by the recognition unit.