PURPOSE: To obtain a device of measuring distance which enables accurate measurement of distance.

CONSTITUTION: An emission signal generated by a control circuit 3 is amplified by an emission drive circuit 2 and a measuring light is emitted from a light- emitting diode 1 to an object of detection. Simultaneously with the emission, the measuring light is inputted to a photodiode 4 through an optical fiber 50 and inputted from it to a counter circuit 6 as a reception signal 0 through a light-receiving circuit 5. A reflected light from the object of detection is also inputted to the counter circuit 6 as a reception signal 1 through the photodiode 4 and the light-receiving circuit 5. Based on the input of the reception signal 0, the counter circuit 6 starts count of clock timing from a count clock 7 and continues the count till the input of the reception signal 1. The number of clock timings from the reception signal 0 to the reception signal 1 is outputted to the control circuit 3 and the distance to the object of detection is calculated on the basis of this number.