Recently, we have developed a transmission-type polarized electron sources (PES)s for the generation of a high brightness beam. The developed PES can applied the extraction voltage of 20 kV at 4 mm electrode-gap and enables to realize the source beam radius of a few micro meter. As the results of prototype gun experiments, the brightness of ∼2 × 107 A.cm−2.sr−1 and a charge density lifetime of 1.8 × 108 C.cm−2 were obtained. A maximum polarization of ~90 % and quantum efficiency of 0.09 % was achieved simultaneously using the transmission photocathode with GaAs-GaAsP strained superlattice layers. Up to now, another two electron gun was manufactured, and those mechanical designs are almost same as that of the prototype. The prototype gun and the second gun have been already operated for the photocathode R&D and for the Spin-LEEM application, respectively. In the near future, further experiments are prepared by using the third gun.