A bearing device for a wheel, comprising: a bearing for a wheel provided with an outer member having double row raceway surfaces (26, 27) in an inner periphery thereof, an inner member (1, 24) having in an outer periphery thereof double row raceway surfaces (28, 29) opposed to the raceway surfaces (26, 27) and having in the outer periphery thereof a flange for mounting a wheel, and configured of a hub and an inner ring fit-engaged with a step portion on an outer peripheral surface of the hub, and a plurality of rolling elements provided between the raceway surfaces (26, 27) of the outer member and the inner member (1, 24); and a constant velocity universal joint having an outer joint member, with a shaft portion of the outer joint member being fitted into a hole of the hub and being connected with the hub through fit-engagement of a recess and a projection, wherein an axially extending plurality of projections is provided either on the shaft portion of the outer joint member or on the hole of the hub, and wherein the shaft portion is press-fitted into the hole of the hub, characterized in that a recess is cut by the projection in either the hole of the hub or in the shaft portion of the outer joint member, to thereby form a recess/projection fit-engagement structure in which the projection and the recess are held in close contact with each other over an entire fit-engagement region to integrate the hub and the outer joint member with each other, in that a press-fitting margin Δd of the projection with respect to a member in which the recess is to be formed and a height h of the projection are in the following relationship: 0.3 < Δd/2h < 0.86 in that, in a pitch circle of the projection, an angle 02 made by a radial line and a side surface of the projection satisfies the following relationship: 20° < 02 < 35°, and when a pitch circle diameter of the projection is PCD, a number of the projections is Z, and P = PCD/Z, P satisfies the following relationship: 0.33 < P < 0.7, and in that a bevelling at an edge of a press-fitting start side end surface of the projection is 0.1 mm or less. a bearing for a wheel provided with an outer member having double row raceway surfaces (26, 27) in an inner periphery thereof, an inner member (1, 24) having in an outer periphery thereof double row raceway surfaces (28, 29) opposed to the raceway surfaces (26, 27) and having in the outer periphery thereof a flange for mounting a wheel, and configured of a hub and an inner ring fit-engaged with a step portion on an outer peripheral surface of the hub, and a plurality of rolling elements provided between the raceway surfaces (26, 27) of the outer member and the inner member (1, 24); and a constant velocity universal joint having an outer joint member, with a shaft portion of the outer joint member being fitted into a hole of the hub and being connected with the hub through fit-engagement of a recess and a projection, wherein an axially extending plurality of projections is provided either on the shaft portion of the outer joint member or on the hole of the hub, and wherein the shaft portion is press-fitted into the hole of the hub, characterized in that a recess is cut by the projection in either the hole of the hub or in the shaft portion of the outer joint member, to thereby form a recess/projection fit-engagement structure in which the projection and the recess are held in close contact with each other over an entire fit-engagement region to integrate the hub and the outer joint member with each other, in that a press-fitting margin Δd of the projection with respect to a member in which the recess is to be formed and a height h of the projection are in the following relationship: 0.3 < Δd/2h < 0.86 in that, in a pitch circle of the projection, an angle 02 made by a radial line and a side surface of the projection satisfies the following relationship: 20° < 02 < 35°, and when a pitch circle diameter of the projection is PCD, a number of the projections is Z, and P = PCD/Z, P satisfies the following relationship: 0.33 < P < 0.7, and in that a bevelling at an edge of a press-fitting start side end surface of the projection is 0.1 mm or less.