A power supply device of an electronic apparatus includes: a power input portion configured to receive alternating current (AC) power; a rectifier-smoother configured to rectify and smooth the received AC power and output the AC power; a power converter configured to convert a level of a voltage output from the rectifier-smoother to supply operating power to the electronic apparatus; a board on which the power input portion, the rectifier-smoother, and the power converter are provided; and a waterproof coating layer formed in an area on the board corresponding to a position of the power converter to prevent infiltration of moisture from an outside.