The photocurrent of sintered AgBr microcrystals of high dark conductivity has been measured at room temperature by using a polarization technique of mobile silver ions. Under the condition in which mobile silver ions were polarized, first, a negative photocurrent was observed and, consequently, this negative photocurrent was reversed to a positive one; that is, a ’’photocurrent‐inversion effect’’ has been found. This negative photocurrent and the inversion effect of the current were explained by the theory of photographic sensitivity and the experimental estimation of the range of photoelectrons (?5×10−4cm) in this sintered AgBr. It has been concluded that excess silver ions could be regarded not only as being significant for the electron traps in the surface region, but also as being the electron traps whose distribution could be varied by external voltage.