To clarify transport properties of the low carrier concentration system Yb4As3 in more detail, we prepared single crystals of Yb4(As1−xSex)3 (x=0.01, 0.05). We expected substituting Se for As to dope electrons into the system. The result of X-ray powder diffraction and magnetic susceptibility measurements indicates that substituting Se may cause a valence change from Yb3+ into Yb2+.