A tripod constant velocity universal joint comprising: an outer joint member having three, cicumferentially equispaced, axially extending track grooves formed in an inner circumference thereof, the outer joint member being connected to a first rotary shaft for transmission of torque; an inner joint member having a boss connected to a second rotary shaft for transmission of torque, three circumferentially equispaced journals each radially protruding from the boss and journal bottom parts each connecting a respective one of the journals to the boss, wherein each journal bottom part consists of a concave portion having a concave curvature in every plane including an axis of the respective journal; and a roller cassette interposed between the outer joint member and the inner joint member for transmission of torque, and an inner roller to be engaged with the journal of the roller cassette, wherein for each journal: a first radius of curvature (Rl) of the concave portion of the respective journal bottom part as viewed in a plane including an axis of the journal but perpendicular to an axis of the inner joint member is larger than a second radius of curvature of the concave portion of the respective journal bottom part as viewed in a plane including the axes of the inner joint member and the journal and characterised in that the radius of curvature of the concave portion of the journal bottom part gradually decreases from the first radius down to the second radius; and the roller cassette, and the inner roller in particular, is mounted to the respective journal of the inner joint member with the roller cassette being inclined by an angle (θ) with respect to the axis of the journal in the plane including the axes of the inner joint member and of the journal, wherein a projected maximum diameter of the journal as viewed in the direction of the angle (θ) of the journal including the outermost part of a protuberant part of a forging parting line is set to be smaller than an inner diameter (d) of the inner roller to be engaged with the journal, of the roller cassette. an outer joint member having three, cicumferentially equispaced, axially extending track grooves formed in an inner circumference thereof, the outer joint member being connected to a first rotary shaft for transmission of torque; an inner joint member having a boss connected to a second rotary shaft for transmission of torque, three circumferentially equispaced journals each radially protruding from the boss and journal bottom parts each connecting a respective one of the journals to the boss, wherein each journal bottom part consists of a concave portion having a concave curvature in every plane including an axis of the respective journal; and a roller cassette interposed between the outer joint member and the inner joint member for transmission of torque, and an inner roller to be engaged with the journal of the roller cassette, wherein for each journal: a first radius of curvature (Rl) of the concave portion of the respective journal bottom part as viewed in a plane including an axis of the journal but perpendicular to an axis of the inner joint member is larger than a second radius of curvature of the concave portion of the respective journal bottom part as viewed in a plane including the axes of the inner joint member and the journal and characterised in that the radius of curvature of the concave portion of the journal bottom part gradually decreases from the first radius down to the second radius; and the roller cassette, and the inner roller in particular, is mounted to the respective journal of the inner joint member with the roller cassette being inclined by an angle (θ) with respect to the axis of the journal in the plane including the axes of the inner joint member and of the journal, wherein a projected maximum diameter of the journal as viewed in the direction of the angle (θ) of the journal including the outermost part of a protuberant part of a forging parting line is set to be smaller than an inner diameter (d) of the inner roller to be engaged with the journal, of the roller cassette. a first radius of curvature (Rl) of the concave portion of the respective journal bottom part as viewed in a plane including an axis of the journal but perpendicular to an axis of the inner joint member is larger than a second radius of curvature of the concave portion of the respective journal bottom part as viewed in a plane including the axes of the inner joint member and the journal and characterised in that the radius of curvature of the concave portion of the journal bottom part gradually decreases from the first radius down to the second radius; and the roller cassette, and the inner roller in particular, is mounted to the respective journal of the inner joint member with the roller cassette being inclined by an angle (θ) with respect to the axis of the journal in the plane including the axes of the inner joint member and of the journal, wherein a projected maximum diameter of the journal as viewed in the direction of the angle (θ) of the journal including the outermost part of a protuberant part of a forging parting line is set to be smaller than an inner diameter (d) of the inner roller to be engaged with the journal, of the roller cassette.