A one-way snap-in cage for a deep groove ball bearing having an annular backbone portion and a hanging out portion extending from the backbone portion towards an axial side. The hanging out portion including a pocket for accommodating a rolling element of a bearing in a circumferential direction and a pocket connection used to connect adjacent pockets. A bottom portion of the pocket is formed integrally with the backbone portion. The ratio Hc/Dw of a radial size Hc of the cage in terms of thickness to the diameter Dw of the rolling element of the bearing satisfies the relation 17.679%≤Hc/Dw≤37.389%, the radial size Hc of the cage is equal in value to half of the difference between the maximum outer diameter Dc_max and the minimum inner diameter Dc_min of the cage. The present invention further provides a deep groove ball bearing using the cage.