A power supply device includes a first power module including a first printed circuit board in which a first protrusion part is formed along a first side surface of the first printed circuit board facing a first direction, a second power module including a second printed circuit board in which a first groove is formed along a second side surface of the printed circuit board facing the first side surface of the first printed circuit board in a second direction, and a third power module including a third printed circuit board electrically connecting the first printed circuit board and the second printed circuit board. The first protrusion part is inserted into the first groove to physically connect the first printed circuit board to the second printed circuit board.