A shroud of a propeller fan being an axial fan, comprising: a body portion for accommodating a rotary vane wheel of the propeller fan; a mount positioned at a center of the body portion for supporting rotary vane wheel driving means for driving the rotary vane wheel; and multiple support beams (10, 10a, 10b, 10c, 10d) radially extending from the mount for joining the mount and the body portion, wherein each of the support beams (10, 10a, 10b, 10c, 10d) becomes thicker from an upstream side of a flow direction of air discharged by the rotary vane wheel toward a downstream side thereof, an edge portion (10 to) of each of the support beams (10, 10a, 10b, 10c, 10d) on the downstream side of the flow direction of the air discharged by the rotary vane wheel is oriented in a direction parallel to a rotation axis (Zf) of the rotary vane wheel, and the edge portion (10 ti, 10 cti) of each of the support beams (10, 10a, 10b, 10c, 10d) on the upstream side of the flow direction of the air discharged by the rotary vane wheel is oriented in a direction opposite to a rotation direction of the rotary vane wheel, characterized in that each of the support beams (10, 10a, 10b, 10c, 10d) has a cross sectional form formed of: two envelopes (SC 1, SC 2) of circles (C1, C2, C3, Cn) arranged on an arc about a virtual center point, the circles (C1, C2, C3, Cn) having different radii decreasing from a downstream end to an upstream end of the arc, the arc being a center line of a cross section of each of the support beams (10, 10a, 10b, 10c, 10d), the cross section being orthogonal to a longitudinal direction of each of the support beams (10, 10a, 10b, 10c, 10d); an arc of a most downstream one of the circles; and an arc of a most upstream one of the circles. a body portion for accommodating a rotary vane wheel of the propeller fan; a mount positioned at a center of the body portion for supporting rotary vane wheel driving means for driving the rotary vane wheel; and multiple support beams (10, 10a, 10b, 10c, 10d) radially extending from the mount for joining the mount and the body portion, wherein each of the support beams (10, 10a, 10b, 10c, 10d) becomes thicker from an upstream side of a flow direction of air discharged by the rotary vane wheel toward a downstream side thereof, an edge portion (10 to) of each of the support beams (10, 10a, 10b, 10c, 10d) on the downstream side of the flow direction of the air discharged by the rotary vane wheel is oriented in a direction parallel to a rotation axis (Zf) of the rotary vane wheel, and the edge portion (10 ti, 10 cti) of each of the support beams (10, 10a, 10b, 10c, 10d) on the upstream side of the flow direction of the air discharged by the rotary vane wheel is oriented in a direction opposite to a rotation direction of the rotary vane wheel, characterized in that each of the support beams (10, 10a, 10b, 10c, 10d) has a cross sectional form formed of: two envelopes (SC 1, SC 2) of circles (C1, C2, C3, Cn) arranged on an arc about a virtual center point, the circles (C1, C2, C3, Cn) having different radii decreasing from a downstream end to an upstream end of the arc, the arc being a center line of a cross section of each of the support beams (10, 10a, 10b, 10c, 10d), the cross section being orthogonal to a longitudinal direction of each of the support beams (10, 10a, 10b, 10c, 10d); an arc of a most downstream one of the circles; and an arc of a most upstream one of the circles. an arc of a most downstream one of the circles; and an arc of a most upstream one of the circles.