There are provided a higher-performance compound semiconductor epitaxial substrate having improved electron mobility characteristics and its production method. The compound semiconductor epitaxial substrate includes a channel layer in which electrons travel and an epitaxial layer on each of a front side and a back side of the channel layer, wherein a total p-type carrier concentration A (/cm2) per unit area in the epitaxial layer on the back side of the channel layer and a total p-type carrier concentration B (/cm2) per unit area in the epitaxial layer on the front side of the channel layer satisfy the following expression (1): 0