A manufacturing method of an SiC epitaxial substrate of an embodiment includes performing a first and a second process alternately to form an n type SiC layer, the first process forming a first SiC layer with an epitaxial growth process by using a first source gas containing an n type impurity, and the second process forming a second SiC layer with an epitaxial growth process by using a second source gas containing the n type impurity, the second source gas having a higher atomic ratio between C (carbon) and Si (silicon) (C/Si) than that of the first source gas, a thickness of the second SiC layer being smaller than a thickness of the first SiC layer.