PURPOSE: To prevent early collapse of protuberances at the application of compressive load by forming a mass concentration consisting of protuberances each having a predetermined length and indentations between two separate areas on the front and back of an annular body.

CONSTITUTION: This pre-load indicating washer comprises an annular body 20 and a plurality of pairs of protuberances 26 and indentations 30. The pre-load indicating washer has a radius of curvature where the mass of material is concentrated along central regions between the inner surface 46 of each indentation 30 and the outer surface 36 of the associated protuberance 26 and between the outer wall parts 38, 40 of each protuberance 26 and the inner wall parts 48, 50 of each indentation 30. Thus, the thickness of material between the inner surface 46 of each indentation 30 and the outer surface 36 of each protuberance 26 is less than at the central region of the combination of each protuberance 26 and each indentation 30. Therefore, the protuberances 26 are elastically deformed and pushed into the indentations 30 during the application of compressive load and do not undergo plastic deformation, whereby premature collapse of the protuberances can be prevented.