A floating bush bearing device (1, 1a to 1e) which rotatably supports a rotation shaft, the floating bush bearing device (1, 1a to 1e) comprising: a bearing housing; a floating bush rotatably disposed between the rotation shaft and an inner circumferential surface of the bearing housing, in the bearing housing; and a bush side oil supply hole extending in a radial direction which is formed through the floating bush and is capable of supplying lubricating oil between the rotation shaft and the inner circumferential surface of the floating bush, wherein an inner circumferential surface of the floating bush has a multi-arc shape formed by combining a plurality of circular-arcs, with different center points so that a gap portion (g) is formed between the rotation shaft and the inner circumferential surface of the floating bush, the gap portion (g) having a predetermined clearance or larger regardless of relative positions of the rotation shaft and the inner circumferential surface of the floating bush, characterised in that an outer circumferential surface of the floating bush has a multi-arc shape formed by combining a plurality of circular-arcs, with different center points so that a gap portion (g') is formed between the inner circumferential surface of the bearing housing and the outer circumferential surface of the floating bush, said gap portion (g') having a predetermined clearance or larger regardless of the position of the floating bush, and the bush side oil supply hole extending in the radial direction communicates with the gap portion (g), that is formed between the rotation shaft and the inner circumferential surface of the floating bush and with the gap portion (g'), that is formed between the inner circumferential surface of the bearing housing and the outer circumferential surface of the floating bush, so that a lubricating oil is stably supplied to the inner side of the floating bush regardless of the position of the rotation shaft and the floating bush. a bearing housing; a floating bush rotatably disposed between the rotation shaft and an inner circumferential surface of the bearing housing, in the bearing housing; and a bush side oil supply hole extending in a radial direction which is formed through the floating bush and is capable of supplying lubricating oil between the rotation shaft and the inner circumferential surface of the floating bush, wherein an inner circumferential surface of the floating bush has a multi-arc shape formed by combining a plurality of circular-arcs, with different center points so that a gap portion (g) is formed between the rotation shaft and the inner circumferential surface of the floating bush, the gap portion (g) having a predetermined clearance or larger regardless of relative positions of the rotation shaft and the inner circumferential surface of the floating bush, characterised in that an outer circumferential surface of the floating bush has a multi-arc shape formed by combining a plurality of circular-arcs, with different center points so that a gap portion (g') is formed between the inner circumferential surface of the bearing housing and the outer circumferential surface of the floating bush, said gap portion (g') having a predetermined clearance or larger regardless of the position of the floating bush, and the bush side oil supply hole extending in the radial direction communicates with the gap portion (g), that is formed between the rotation shaft and the inner circumferential surface of the floating bush and with the gap portion (g'), that is formed between the inner circumferential surface of the bearing housing and the outer circumferential surface of the floating bush, so that a lubricating oil is stably supplied to the inner side of the floating bush regardless of the position of the rotation shaft and the floating bush.