PURPOSE: To attain to reduce the number of parts and the number of adjusting processes and to enhance the preciseness and the reliability of the titled apparatus, by using a high speed multiple phase shift time sharing system to enable the measurement available and unavailable electric energy by one time sharing multiply circuit.

CONSTITUTION: A signal ev proportional to the load voltage of a current supply wire taken out by a transformer 21 for a measuring instrument divided into two branches and one of them is introduced into the side of the switch part S of a switch circuit S1 while the other is introduced into the other switch part S' in a state delaying a phase by π/2 by a phase shift circuit 23. Because the switch parts S, S' are alternately turned on and off by the high speed time sharing pulse from a time sharing pulse distributor 24, signals ev, e'v are alternately supplied to a pulse width modulation circuit 22 by the operation of the circuit S1. The circuit 22 performs pulse width modulation by using the signals ev, e'v to fabricate a pulse width duty cycle signal which is, in turn, introduced into a time sharing multiply circuit 28. This circuit 28 takes in a signal ei proportional to the consumption current of a power supply line to perform the multiplication of ev, ei, e'v, e'i. This signal is converted to pulse frequency to display available and unavailable electric energy by display parts 35, 36.