PURPOSE: To provide a method for observing or photographing a diamond, which can acquire the brightness state of the diamond clearly based on the good or bad state of a cut and can simply judge the good or bad state of the cut of the diamond simply even by a novice.

CONSTITUTION: A light source 2 is arranged in an approximately symmetry pattern with the axial extension line of a diamond 1 as the center or so as to surround the axial extension line at a position, which is separated by an suitable interval from the diamond 1. The position is located in the range of 21°-39°, preferably 24°-36°, with the diamond 1 to be observed or photographed as the center. The diamond 1 is observed or photographed (a) from the opposite direction with respect to the diamond 1 with the light source 2 in-between.