Electronic properties of small silicon clusters (n≤11), produced by a laser vaporization method, were investigated by photoelectron spectroscopy of their anions. The doping of F or Na atoms enables us to substract or add an electron from/into the silicon clusters without any serious geometric rearrangement, revealingelectronic structures of the silicon clusters. Both the doped F and Na atoms areattached onto the surface of the silicon clusters, which is in agreement with abinitio theoretical calculation on electronic and geometric structures of the Si-F and Si-Na binary clusters. The cluster size dependence of HOMO-LUMO gaps in the neutral silicon clusters were measured experimentally with the F atom doping, and the electronic structures above the LUMO of the neutral silicon clusters were revealed with the Na atom doping. The doping of C atoms, furthermore, induces some geometric change of the silicon clusters, and the substitution of Si atoms to C atoms results in a phase transition.