PURPOSE: To measure signal waveforms continuously in real time by dividing the pulse width of a signal to be measured into a plurality of parts, and performing counting measurement.

CONSTITUTION: A receiver circuit 1 receives a signal to be measured 101. A signal dividing device 2 receives the output signal from the circuit 1 and outputs pulse width signals 102-1 and 102-2. Delay pulse generators 3-1 and 3-2 receive the signal 102-1 and 102-2, delay the signals by a specified times and output a plurality of delayed signals. A 1/N frequency divider 13 divides the oscillating frequency from an oscillator 12 and sends out a clock signal. Each of gate circuits 4-1 and 4-2 receives one delayed signal and the clock signal. Counting circuits 5-1 and 5-2 receive the output signals of the circuits 4-1 and 4-2 and the other delayed signal and perform counting measurement. Registers 6-1 and 6-2 store the counted values together with bit-wait during each counting measurement. A microprocessor 9 compiles the measured data in each register and displays the result on a display 10.