A power supply mounting apparatus includes a chassis (40), a mounting board (20) attached to the power supply, and a mounting bracket (30). The chassis includes a rear panel (50) with an opening (52), and first and second side panels (50, 70). The mounting board forms a pair of mounting hooks (25) at each side thereof. The mounting bracket includes two mounting portions (31, 32) and a connecting portion (33). Each mounting portion defines slits (35) and locking holes (36). The rear panel forms catches slidably engaging in the locking holes. After the power supply slides in the chassis with the mounting hooks extending in the corresponding slits, the mounting bracket is moved horizontally so that the hooks hook the rear panel. The second side panel is attached to the chassis to prevent the mounting bracket from leaving the chassis.