A tapered land thrust bearing device, comprising: a rotary shaft ; a flange portion fitted onto the rotary shaft and including a first thrust portion ; and a thrust member including a through hole through which the rotary shaft is inserted and a second thrust portion which is disposed around the through hole and which faces the first thrust portion of the flange portion , wherein one of the first thrust portion or the second thrust portion includes a plurality of land surfaces each of which is parallel to a plane orthogonal to an axis of the rotary shaft , the land surfaces being disposed at intervals in a circumferential direction of the through hole , a plurality of tapered surfaces each of which is disposed between the plurality of land surfaces , joined via a step to a boundary of the land surface on one side in the circumferential direction of the through hole , and joined continuously to a boundary of the land surface on the other side in the circumferential direction of the through hole , and wherein one of the first thrust portion or the second thrust portion further includes an annular surface which extends along outer circumferential edges of the land surfaces and outer circumferential edges of the tapered surfaces in the circumferential direction of the through hole , characterized in that at least one concave portion is disposed on each of the plurality of land surfaces , and a surface roughness of the land surfaces is greater than a surface roughness of the annular surface by forming a plurality of microscopic holes on each of the plurality of land surfaces , whereby each of the plurality of microscopic holes has a depth which is 1/10 to 1/100 times a depth of the at least one concave portion . a rotary shaft ; a flange portion fitted onto the rotary shaft and including a first thrust portion ; and a thrust member including a through hole through which the rotary shaft is inserted and a second thrust portion which is disposed around the through hole and which faces the first thrust portion of the flange portion , wherein one of the first thrust portion or the second thrust portion includes a plurality of land surfaces each of which is parallel to a plane orthogonal to an axis of the rotary shaft , the land surfaces being disposed at intervals in a circumferential direction of the through hole , a plurality of tapered surfaces each of which is disposed between the plurality of land surfaces , joined via a step to a boundary of the land surface on one side in the circumferential direction of the through hole , and joined continuously to a boundary of the land surface on the other side in the circumferential direction of the through hole , and a plurality of land surfaces each of which is parallel to a plane orthogonal to an axis of the rotary shaft , the land surfaces being disposed at intervals in a circumferential direction of the through hole , a plurality of tapered surfaces each of which is disposed between the plurality of land surfaces , joined via a step to a boundary of the land surface on one side in the circumferential direction of the through hole , and joined continuously to a boundary of the land surface on the other side in the circumferential direction of the through hole , and wherein one of the first thrust portion or the second thrust portion further includes an annular surface which extends along outer circumferential edges of the land surfaces and outer circumferential edges of the tapered surfaces in the circumferential direction of the through hole , characterized in that at least one concave portion is disposed on each of the plurality of land surfaces , and a surface roughness of the land surfaces is greater than a surface roughness of the annular surface by forming a plurality of microscopic holes on each of the plurality of land surfaces , whereby each of the plurality of microscopic holes has a depth which is 1/10 to 1/100 times a depth of the at least one concave portion . <EOS>