1. A defect classifying method that detects a defect which is present at a silicon carbide substrate and classifies the defect by distinguishing a basal plane dislocation from other crystal defects, the defect classifying method comprising: projecting an illumination beam toward the silicon carbide substrate and scanning the silicon carbide substrate with the illumination beam; condensing reflected light and photoluminescence light emitted from the silicon carbide substrate; separating, from the condensed light, each of reflected light and photoluminescence light of a visible region or an infrared region, and detecting each of the reflected light and the photoluminescence light of the visible region or the infrared region; a first inspection step of detecting a defect from the detected reflected light and detecting a defect image of the reflected light; a second inspection step of detecting a defect from the detected photoluminescence light and detecting a defect image of the photoluminescence light; and a defect classification step of classifying each defect detected in the first and second inspection steps, wherein when the defect image of the photoluminescence light is detected in the second inspection step, the defect is classified with reference to a result of a reflected light inspection in the first inspection step.