A single-split cage for continuously holding a plurality of rolling elements stably for a long time. 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, and 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.