A wheel bearing apparatus comprising: an outer member (2 or 18) integrally formed on its outer circumference with a body mounting flange and on its inner circumference with double row outer raceway surfaces (2a; 2a or 2a; 18a); an inner member (1, 17 or 22) including a hub wheel (4, 19 or 23) and an inner ring (5 or 20), the hub wheel (4, 19 or 23) being integrally formed on its one end with a wheel mounting flange and on its outer circumference with one inner raceway surface opposing to one of the outer raceway surfaces (2a or 2a) and having a cylindrical portion (4b, 19a or 23a) axially extending from the inner raceway surface through a stepped portion, the inner ring (5 or 20) being formed on its outer circumference respectively with the other inner raceway surface (5a or 20a) opposing to the other of the double row outer raceway surfaces (2a or 18a); double row rolling elements (3 and 3) rollably contained between the inner raceway surfaces (4a; 5a or 4a; 20a) of the inner member (1, 17 or 22) and the outer raceway surfaces (2a; 2a or 2a; 18a) of the outer member (2 or 18); and the inner ring being axially immovably secured on the hub wheel (4,19 or 23) by a caulking portion formed by plastically deforming radially outward an end of the cylindrical portion (4b, 19a or 23a) of the hub wheel (4, 19 or 23), and that the thickness (h1 or h2) of a smaller end surface (5b or 20b) of the inner ring (5 or 20) is larger than the height of the stepped portion of the hub wheel (4, 19 or 23); that the axial position of the smaller end surface (5b or 20b) of the inner ring (5 or 20) is set within an axial range between the axial position of the outermost-side point of the inner-side rolling elements of the double row rolling elements (3 and 3) and the axial position of the groove bottom point of the inner raceway surface (5a or 20a) of the inner ring (5 or 20); and characterised in that a value obtained by dividing a dimensionless value of the area (A1 or A2) of the smaller end surface (5b or 20b) of the inner ring (5 or 20) by a dimensionless value of the inner diameter (d) of the inner ring (5 or 20) is set to 11 or more. an outer member (2 or 18) integrally formed on its outer circumference with a body mounting flange and on its inner circumference with double row outer raceway surfaces (2a; 2a or 2a; 18a); an inner member (1, 17 or 22) including a hub wheel (4, 19 or 23) and an inner ring (5 or 20), the hub wheel (4, 19 or 23) being integrally formed on its one end with a wheel mounting flange and on its outer circumference with one inner raceway surface opposing to one of the outer raceway surfaces (2a or 2a) and having a cylindrical portion (4b, 19a or 23a) axially extending from the inner raceway surface through a stepped portion, the inner ring (5 or 20) being formed on its outer circumference respectively with the other inner raceway surface (5a or 20a) opposing to the other of the double row outer raceway surfaces (2a or 18a); double row rolling elements (3 and 3) rollably contained between the inner raceway surfaces (4a; 5a or 4a; 20a) of the inner member (1, 17 or 22) and the outer raceway surfaces (2a; 2a or 2a; 18a) of the outer member (2 or 18); and the inner ring being axially immovably secured on the hub wheel (4,19 or 23) by a caulking portion formed by plastically deforming radially outward an end of the cylindrical portion (4b, 19a or 23a) of the hub wheel (4, 19 or 23), and that the thickness (h1 or h2) of a smaller end surface (5b or 20b) of the inner ring (5 or 20) is larger than the height of the stepped portion of the hub wheel (4, 19 or 23); that the axial position of the smaller end surface (5b or 20b) of the inner ring (5 or 20) is set within an axial range between the axial position of the outermost-side point of the inner-side rolling elements of the double row rolling elements (3 and 3) and the axial position of the groove bottom point of the inner raceway surface (5a or 20a) of the inner ring (5 or 20); and characterised in that a value obtained by dividing a dimensionless value of the area (A1 or A2) of the smaller end surface (5b or 20b) of the inner ring (5 or 20) by a dimensionless value of the inner diameter (d) of the inner ring (5 or 20) is set to 11 or more.