To provide a transmission ratio variable apparatus capable of correctly specifying the motor rotational angle even at the re-start after the lock operation.

When an IFSECU selects a "semi-emergency mode" for executing the lock operation after the phase-locked energization as the lock control mode (Step 103: YES), it is determined whether or not a ridge of a lock holder is located at a position corresponding to an engagement part of a lock lever (a sensor pattern [4]) at the time, i.e., at the lock control starting point (Step 104). When the ridge is located at the position corresponding to the engagement part (Step 104: YES), the phase-locked energization is executed so that a part in an engagement groove (the sensor pattern [3]) is stopped at the position corresponding to the engagement part (Step 105), and then a locking device is operated to lock (Step 106).