A power supply apparatus includes a transformer, an electrolytic capacitor provided in primary circuitry of the transformer, a board, and a heat sink having a protruding portion and a cover portion. The electrolytic capacitor includes an explosion-proof valve that opens to cause an electrolytic solution to be jetted from the electrolytic capacitor. The electrolytic capacitor is placed on the board so that a surface of the electrolytic capacitor opposite to a surface on which the explosion-proof valve is provided faces the board. The cover portion has a hole formed in the cover portion and, when the cover portion is viewed in a direction vertical to the surface of the electrolytic capacitor on which the explosion-proof valve is provided, at least the explosion-proof valve and the hole formed in the cover portion do not overlap each other and the cover portion encompasses the explosion-proof valve.