Abstract: An inter-pulse time difference measuring circuit which expands the time difference between a first pulse and a second pulse by a given multiplication factor and measures the expanded time difference, thereby realizing a higher measuring resolution. The circuit can be constructed by using a capacitor charging and discharging circuit connected to a constant current source and such circuit can always expand the time difference by a given multiplication factor even if the voltages and resistance values of the other circuits than the constant current circuit are varied with temperature changes. The circuit can also be realized by a circuit which charges and discharges a capacitor through a pair of transistors having a given current ratio and such circuit can maintain the current ratio of the transistors constant without suffering the effect of temperature changes, thereby always ensuring expansion of the time difference between pulses by a given multiplication factor.