A pair of annular body sliding parts (3, 5) comprising sealing faces that are adapted to relatively slide on each other, wherein: a reversed Rayleigh step mechanism adapted to serve as a negative pressure generation mechanism is provided in at least one of the sealing faces; a negative pressure generation groove that forms the reversed Rayleigh step mechanism is provided in an arc shape along the circumferential direction of the at least one of the sealing faces so as to be isolated from a high-pressure fluid side and a low-pressure fluid side by a land section; an upstream side end and a downstream side end of the negative pressure generation groove are isolated from each other by the land section; the downstream side end communicates with the high-pressure fluid side via a deep groove; and the high-pressure fluid side is an outer peripheral side of the sliding parts (3, 5), and the low-pressure fluid side is an inner peripheral side of the sliding parts (3, 5), characterized in that: only one said reversed Rayleigh step mechanism is provided in the at least one of the sealing faces, said mechanism being formed of only one said negative pressure generation groove and of only one said deep groove, in that a ratio x = b/a between circumferential length a (a1, a2) of the negative pressure generation groove and circumferential length b (b1, b2) of the land section between the upstream side end of the negative pressure generation groove and the deep groove is set to be different in a radial direction, and in that, on the inner peripheral side, the circumferential length b (b1, b2) of the land section between the upstream side end of the negative pressure generation groove and the deep groove is smaller than the outer peripheral side, thus the ratio x being small on the inner diameter side and large on the outer diameter side. a reversed Rayleigh step mechanism adapted to serve as a negative pressure generation mechanism is provided in at least one of the sealing faces; a negative pressure generation groove that forms the reversed Rayleigh step mechanism is provided in an arc shape along the circumferential direction of the at least one of the sealing faces so as to be isolated from a high-pressure fluid side and a low-pressure fluid side by a land section; an upstream side end and a downstream side end of the negative pressure generation groove are isolated from each other by the land section; the downstream side end communicates with the high-pressure fluid side via a deep groove; and the high-pressure fluid side is an outer peripheral side of the sliding parts (3, 5), and the low-pressure fluid side is an inner peripheral side of the sliding parts (3, 5), characterized in that: only one said reversed Rayleigh step mechanism is provided in the at least one of the sealing faces, said mechanism being formed of only one said negative pressure generation groove and of only one said deep groove, in that a ratio x = b/a between circumferential length a (a1, a2) of the negative pressure generation groove and circumferential length b (b1, b2) of the land section between the upstream side end of the negative pressure generation groove and the deep groove is set to be different in a radial direction, and in that, on the inner peripheral side, the circumferential length b (b1, b2) of the land section between the upstream side end of the negative pressure generation groove and the deep groove is smaller than the outer peripheral side, thus the ratio x being small on the inner diameter side and large on the outer diameter side. only one said reversed Rayleigh step mechanism is provided in the at least one of the sealing faces, said mechanism being formed of only one said negative pressure generation groove and of only one said deep groove, in that a ratio x = b/a between circumferential length a (a1, a2) of the negative pressure generation groove and circumferential length b (b1, b2) of the land section between the upstream side end of the negative pressure generation groove and the deep groove is set to be different in a radial direction, and in that, on the inner peripheral side, the circumferential length b (b1, b2) of the land section between the upstream side end of the negative pressure generation groove and the deep groove is smaller than the outer peripheral side, thus the ratio x being small on the inner diameter side and large on the outer diameter side.