A silicon carbide semiconductor substrate according to an aspect of the present disclosure has a first principal surface and a second principal surface opposite to the first principal surface. The silicon carbide semiconductor substrate includes a silicon carbide semiconductor crystal, and a first affected layer having crystal disturbances and disposed under the first principal surface. A thickness of the first affected layer in a first region including a center of the first principal surface is smaller than a thickness of the first affected layer in a second region surrounding the first region in a plane view.