The electronic flash unit disclosed comprises: a transformer (14) to vary voltages of a power supply; an accumulator (16) composed of a main capacitor (17) to charge an electric energy supplied from the transformer (14); a lamp unit (4) provided with a flashlamp (20), set inside of a reflector (19), that flashes by discharging of energy storages in the main capacitor (17) upon applying a voltage on a trigger terminal (21); and a trigger circuit (10) to generate the voltage to apply on the trigger terminal (21), wherein at least the lamp unit (4) is coated with an insulation material.