Optical print head includes: light-emitting elements connected one-to-one to current supply lines branching from first power line at different positions in longitudinal direction,holding elements,signal writing unit writing luminance signal into each holding element, the luminance signal being represented by voltage indicating light emission amount of corresponding light-emitting element,second power line supplying reference voltage to each holding element, the reference voltage being reference when signal writing unit writes luminance signal into holding element,and driving drivers corresponding one-to-one with current supply lines and controlling current supplied to corresponding current supply line from first power line, in accordance with voltage held in corresponding holding element when signal writing unit has written luminance signal into corresponding holding element, wherein power source supplying the reference voltage to second power line is common with power source supplying voltage to signal output subunit outputting luminance signal.