An imaging forming apparatus includes a positive high-voltage circuit that generates voltage having a positive polarity, a negative high-voltage circuit connected in series with the positive high-voltage circuit and generates voltage having a negative polarity, a transfer roller to which the voltage generated by the positive high-voltage circuit or the negative high-voltage circuit is supplied, neutralizing pins to which the voltage generated by the negative high-voltage circuit is supplied, a current detection circuit that detects current flowing into the transfer roller, and a diode connected between the transfer roller and the neutralizing pins and that separates a path for the current flowing into the transfer roller and a path for current flowing into the neutralizing pins from each other.