A method for starting single phase induction motor using an electronic relay, the electronic relay comprising: a triac connected between a start winding and start capacitor (Cs) of the single phase induction motor to control a current flow of the start winding; a discharge circuit for discharging a charge voltage of the start capacitor (Cs); an induced voltage detection circuit detecting an induced voltage of the start winding; a window comparison circuit detecting a both-end voltage of the triac to detect a zero-point voltage of a motor line voltage before start and to detect a zero-point current of a start winding current during start; and a Micro Control Unit: turning on the triac at the zero-point voltage of the motor line voltage to begin starting according to a signal of the window comparison circuit, triggering a gate of the triac for a certain delay time at every zero-point current time of the start winding current to maintain a turn-on state of the triac according to the signal of the window comparison circuit during start, receiving the induced voltage of the start winding from the induced voltage detection circuit to calculate a variation rate of the induced voltage during start, checking when a start torque is maximum which corresponds with a maximum acceleration torque, and turning off the triac when the acceleration torque begins decreasing; the method comprising: turning on the triac to flow a current in a start winding; detecting from the start winding an induced voltage when a current flows in the start winding; receiving the detected induced voltage to calculate a variation rate of the induced voltage, and storing the calculated variation rate; comparing the stored variation rate of the induced voltage, and determining a time when the variation rate of the induced voltage is the maximum as a time when a start torque is the maximum, when the variation rate of the induced voltage increases and then decreases; and turning off the triac by limiting a gate current of the triac to complete start, when the variation rate of the induced voltage begins decreasing after the determination. a triac connected between a start winding and start capacitor (Cs) of the single phase induction motor to control a current flow of the start winding; a discharge circuit for discharging a charge voltage of the start capacitor (Cs); an induced voltage detection circuit detecting an induced voltage of the start winding; a window comparison circuit detecting a both-end voltage of the triac to detect a zero-point voltage of a motor line voltage before start and to detect a zero-point current of a start winding current during start; and a Micro Control Unit: turning on the triac at the zero-point voltage of the motor line voltage to begin starting according to a signal of the window comparison circuit, triggering a gate of the triac for a certain delay time at every zero-point current time of the start winding current to maintain a turn-on state of the triac according to the signal of the window comparison circuit during start, receiving the induced voltage of the start winding from the induced voltage detection circuit to calculate a variation rate of the induced voltage during start, checking when a start torque is maximum which corresponds with a maximum acceleration torque, and turning off the triac when the acceleration torque begins decreasing; turning on the triac at the zero-point voltage of the motor line voltage to begin starting according to a signal of the window comparison circuit, triggering a gate of the triac for a certain delay time at every zero-point current time of the start winding current to maintain a turn-on state of the triac according to the signal of the window comparison circuit during start, receiving the induced voltage of the start winding from the induced voltage detection circuit to calculate a variation rate of the induced voltage during start, checking when a start torque is maximum which corresponds with a maximum acceleration torque, and turning off the triac when the acceleration torque begins decreasing; turning on the triac to flow a current in a start winding; detecting from the start winding an induced voltage when a current flows in the start winding; receiving the detected induced voltage to calculate a variation rate of the induced voltage, and storing the calculated variation rate; comparing the stored variation rate of the induced voltage, and determining a time when the variation rate of the induced voltage is the maximum as a time when a start torque is the maximum, when the variation rate of the induced voltage increases and then decreases; and turning off the triac by limiting a gate current of the triac to complete start, when the variation rate of the induced voltage begins decreasing after the determination.