The photoconductivity of boron doped a—SiNx:H(x=O.07)has been studied by steady state secondary photocurrent, xerographic photodischarge, the time of flight measurement, and ESR. The dominant carrier of the photocurrent in a—SiNx:H is found to be electron. The μτ product of the electron decreases with increasirg doping amount of boron, while that of the hole increases and becomes largerthan 10-8cm2/V. From these results it is found that the life time of the hole becomes longer with increasing the amount of doping boron. The intensity of the ESR signal due to the neutral dangling bonds decreases monotonically with doping boron, and this decrease of the neutral dangling bond density is considered to be due to not only change of the occupation statistics, but mainly to the chemical or electrical interaction between boron and nitrogen.