A mounting apparatus for power supply includes a chassis for carrying a power supply, a computer case, and a securing bracket. A pivot portion is formed on the chassis. The computer case includes a bottom wall and a rear plate perpendicular to the bottom wall. The rear plate defines a guiding slot for the pivot portion rotating and sliding therein. The securing bracket is mounted to the computer case. The chassis is inter-engaged with the computer case and/or the securing bracket. The securing bracket includes an elastic blocking member blocking an end of the chassis, for preventing the chassis disengaging from the computer case and/or the securing bracket.