A crossed roller bearing, including: an inner element and an outer element that relatively rotate, the inner element including an annular inner V-groove that is provided along an outer peripheral surface of the inner element and that has a V shape that opens towards the outer element, the outer element including an annular outer V-groove that is provided along an inner peripheral surface of the outer element, that has a V shape that opens towards the inner element, and that faces the inner V-groove; a plurality of cylindrical rolling elements that are placed between the inner V-groove and the outer V-groove, that roll while being in contact with the inner V-groove and the outer V-groove, and adjacent rolling elements of which have rolling axes that are perpendicular to each other; and a retainer that are placed between the adjacent rolling elements that includes a flat section that is a projecting central section on an area which faces either one of the rolling elements and that is capable of contact with the rolling element, and a tilt section whose degree of projection becomes smaller as it goes from the flat section to an end section of the retainer.