We observed that the current of a He+ ion beam generated from an RF ion source was enhanced by optical pumping (OP) using 1083 nm resonance radiation. The ion current enhancement became more remarkable with higher pressure and higher OP radiation density. The ion beam current with an OP irradiation of 0.5 W cm−2 at 65 Pa was 1.25 times larger than that without OP. We interpreted this OP effect on the ion current in terms of Penning ionization (PI) of He (23S) by He (23P). From the pressure dependence of the OP effect, we analysed the ratio of the rate constant of PI (RPI) to that of the total ionization process (RTotal). We verified the validity of this analysis for RPI/RTotal from the relationship of spin polarization between He (23S) atoms and He+ ions.