PURPOSE: To obtain a pulse amplitude data sampling circuit which enables highly accurate determination of a pulse amplitude data with the lowering of variations in pulse amplitude sampling data for each input pulse signal even in use under the environment with much noise.

CONSTITUTION: When a pulse width of an input pulse signal 1 exceeds four cycles of a clock, a data at the second clock and that at the third clock are sampled. A mean of the data is outputted as a pulse amplitude sampling data 23. When the pulse width of the input pulse signal 1 is equivalent to three cycles of the clock, the mean of the data at the first clock and that at the second clock is outputted as pulse amplitude sampling data.