A single-split cage for holding a plurality of rolling elements stably by eliminating the difference in the strength between split regions, by maintaining the strength of the entire cage uniform in the circumferential direction and by maintaining the dimensional accuracy between the split regions constant at the time of molding. A split section for splitting at one portion in the circumferential direction is formed at regions extending between pockets adjacent to each other in the circumferential direction, engagement sections being engageable with each other are provided at the circumferential central position between the pockets and on a one-side split face and the other-side split face formed by splitting the regions. In a state in which both the engagement sections are engaged with each other, predetermined clearances are formed between the one-side split face and the other-side split face and between the engagement sections.