A semi-insulating compound semiconductor substrate includes a semi-insulating compound semiconductor, the semi-insulating compound semiconductor substrate being configured such that, on a major plane having a plane orientation of (100), a standard deviation/average value of specific resistance measured at intervals of 0.1 mm along equivalent four directions in a direction from a center of the major plane, and a standard deviation/average value of specific resistance measured at intervals of 0.1 mm along equivalent four directions in a direction from the center of the major plane are each not more than 0.1.