In recent years, study of brain computer interface (BCI) is conducted actively and many researches of implementation using electro encephalic gram (EEG) are reported. On the other hand, near-infrared spectroscopy (NIRS) is noninvasive measurements, but there are many problems remaining unsolved and little is reported about the actual procedures or implementation examples when applying NIRS to realize BCI. We propose a method to quantitatively estimate start and end timing of movement by using a neural network. We measured regional cerebral blood flow during tapping movement of the right hand by NIRS. The following tendencies of total-Hb were observed. Hb increased within 10 s from the movement start time, decreased within 10 s from the movement end time. In this paper, the estimation method showed the possibility of applications to the ON/OFF control of BCI.