A torque adjusting device of an electric drill includes an annular member with notches in an end and grooves in an outer periphery thereof. A driving part connected to an output shaft is received in the annular member and operationally connected to the motor by a solar gear system. A mounting member has pins located in alignment with the grooves and a cap has a ring member movably mounted to the mounting member. A spring is biased between the ring member and the pressing ring which presses balls engaged with the notches. when the ring member is moved to compress the spring, the pins are pushed into the grooves by the ring member to secure the annular member so as to output strong torque.