A self-aligning roller bearing comprising: an outer ring having an outer raceway surface that is a recessed curve on an inner periphery of the outer ring; an inner ring having two rows of inner raceway surfaces that are recessed curves side by side on an outer periphery of the inner ring and having a rib portion at each axially outward end; a plurality of spherical rollers disposed between the outer raceway surface and the inner raceway surface in two rows side by side; a cage having a plurality of pockets that accommodate the spherical rollers to hold each row of the spherical rollers at intervals in a circumferential direction; and a guide ring disposed between the cage and the inner ring as well as between the two rows of the spherical rollers, wherein in a longitudinal section including a center line of the spherical roller and an axis of the self-aligning roller bearing, a clearance X between an outer end surface of the spherical roller on an axially outer side of the self-aligning roller bearing and the rib portion, and a clearance Y between an inner end surface of the spherical roller on an axially inner side of the self-aligning roller bearing and the guide ring have a relation of X < Y, characterized in, that the cage includes an annular member disposed radially outward of the guide ring as well as between the two rows of the spherical rollers, and in the longitudinal section including the center line of the spherical roller and the axis of the self-aligning roller bearing, when a clearance between the axially outer side surface of the annular member and the inner end surface of the spherical roller is regarded as a clearance Z, the clearances Y and Z have a relation of Y < Z. an outer ring having an outer raceway surface that is a recessed curve on an inner periphery of the outer ring; an inner ring having two rows of inner raceway surfaces that are recessed curves side by side on an outer periphery of the inner ring and having a rib portion at each axially outward end; a plurality of spherical rollers disposed between the outer raceway surface and the inner raceway surface in two rows side by side; a cage having a plurality of pockets that accommodate the spherical rollers to hold each row of the spherical rollers at intervals in a circumferential direction; and a guide ring disposed between the cage and the inner ring as well as between the two rows of the spherical rollers, wherein in a longitudinal section including a center line of the spherical roller and an axis of the self-aligning roller bearing, a clearance X between an outer end surface of the spherical roller on an axially outer side of the self-aligning roller bearing and the rib portion, and a clearance Y between an inner end surface of the spherical roller on an axially inner side of the self-aligning roller bearing and the guide ring have a relation of X < Y, characterized in, that the cage includes an annular member disposed radially outward of the guide ring as well as between the two rows of the spherical rollers, and in the longitudinal section including the center line of the spherical roller and the axis of the self-aligning roller bearing, when a clearance between the axially outer side surface of the annular member and the inner end surface of the spherical roller is regarded as a clearance Z, the clearances Y and Z have a relation of Y < Z.