Disclosed is a method of controlling a robot, for restarting the robot by resupplying an electric power in the event of a power failure. When a power failure detection circuit detects that a voltage has dropped or has been cut off, the circuit notifies an operating method (OS) of this (S1) and the OS writes a power failure flag to a non-volatile memory and stops a task being performed (S2). The data of the task being performed is saved in the non-volatile memory. After the electric power has been resupplied (S10), the OS executes a power failure processing for itself, with reference to the power failure flag (S11), initializes hardware (S12), executes a power failure processing routine for each task (S13), and restarts the operation of the robot from the position at which the robot was stopped when the power failure occurred (S14).