We report on the electrical properties of Pt/Nb-doped SrTiO3 single crystal junctions. The junctions showed rectifying current (I) - voltage (V) characteristics, indicating formation of Schottky diodes. The junction also exhibited hysteretic transport behaviors upon polarity reversal. The junction capacitance measured at 1 MHz was much smaller than those at 1 - 100 kHz. The frequency dependence revealed that deep-level trap states existed in the junctions, and that those interface states affected the electrical properties of the junctions significantly.