A distance measuring apparatus using a pulse laser light which has a wide measurement range and can execute high speed operation. The apparatus emits a pulsed light onto an object, receives a reflected pulsed light by a light receiving element, and amplifies an output thereof by a tuning amplifier. A sampling data of a damped oscillation wave form responding to the reflected pulsed light output from the tuning amplifier is added so as to be shifted by one cycle. Accordingly, it is possible to execute an enhancing process of a peak value utilizing a periodicity of the damped oscillation wave form responding to the pulsed signal, and it is possible to improve a detecting sensitivity of the reflected pulsed light.