A single crystal diamond has a surface. In the single crystal diamond, a measurement region is defined in the surface, the measurement region includes a portion exhibiting a transmittance that is highest in the single crystal diamond and a portion exhibiting a transmittance that is lowest in the single crystal diamond, the measurement region has a plurality of square regions that are continuously arranged and each have a side having a length of 0.2 mm, and an average value of transmittances in each of the plurality of square regions is measured, wherein assuming that the average value of the transmittances in one square region is defined as T1 and the average value of the transmittances in another square region adjacent to the one square region is defined as T2, a relation of ((T1−T2)/((T1+T2)/2)×100)/0.2≤20 (%/mm) is satisfied throughout the measurement region.