To reduce the make rate measurement error of a dial pulse even though the impedance of a circuit side changes and to improve measurement accuracy by converting a dial pulse signal into a digital value, monitoring the digital value to perform decision of make or break and measuring a make rate from the results.

When a telephone set transmits a dial pulse being a dial signal A, current is caused to flow into a circuit is changed. The circuit 10 of a testing machine converts the current into a voltage and eliminates chattering and noise through a filter to make it a dial signal B. An analog-to-digital conversion circuit 11 converts the signal B into a digital signal in a prescribed cycle. A processor 12 decides that the digital signal as break in the case the rate of change within fixed time is equal to or more than a fixed value and decides it as make when the rate of change is below the fixed value. The processor 12 reproduces a dial signal D based on these decisions and calculates a make rate based on the reproduced dial signal D.