A roller bearing includes an inner ring having an inner-ring raceway surface on an outer periphery of the inner ring, an outer ring arranged concentric with and peripherally outside the inner ring and having, on an inner periphery of the outer ring, an outer-ring raceway surface that faces the inner-ring raceway surface, a plurality of rollers interposed between the inner-ring raceway surface and the outer-ring raceway surface in a rollable manner, and a cage that holds the rollers at predetermined intervals along a circumferential direction. Opposite end portions of the outer-ring raceway surface in an axial direction serve as guide surfaces or which rotation of the cage is guided. Or an outer periphery of the cage, slidable contact surfaces are formed which slidably contact the guide surfaces and which are arranged to face the respective guide surfaces across a labyrinth clearance.