The invention provides a split cage and a roller bearing. The split cage includes a plurality of cage segments each having a pair of rim portions and a pair of cage bar portions, the cage bar portions and the rim portions defining a single pocket that accommodates a single tapered roller. Turning of each of the cage segments is guided by the tapered roller, the cage segments being arranged in a circular pattern along the circumferential direction of the split cage, in an annular space between inner and outer rings. Each cage segment has projections formed so as to project radially inward from the pocket, and formed at the rim portions. A projecting length of each projection is set to such a length that the projection is brought into contact with an outer peripheral side portion of the inner ring before the cage segment is detached from the tapered roller when the cage segment is displaced to the radially inside.