A wind turbine power generating apparatus, comprising: at least one blade; a hub to which the at least one blade is mounted rotatably; and a spinner disposed so as to cover the hub, wherein the spinner includes a tubular part which extends around a rotational axis of the hub and which has an opening through which the blade extends, wherein the tubular part of the spinner has a shape such that, when an intersection of the tubular part and a virtual cylinder surrounding the opening and extending along a blade root of the blade is projected on a plane including an axis of the blade and the rotational axis, a projection line (32, 32', 32") of the intersection is within a range defined by a reference line connecting opposite ends (40, 42) of the projection line (32, 32', 32") and a reference curve (34, 34', 34") which is an intersection line, projected on the plane, of the virtual cylinder and a locus (21a, 21b) of the reference line rotating about the rotational axis, wherein the tubular part has a bulge at least around the opening, the bulge bulging outward from the locus (21a, 21b) in at least one part of a central region between the opposite ends (40, 42) of the projection line (32, 32' 32") with respect to a direction of the rotational axis of the hub, wherein the tubular part has a cross-sectional contour along a plane orthogonal to the rotational axis of the hub, in the at least one part of the central region, the cross-sectional contour having a distance from the rotational axis which varies in the circumferential direction of the rotational axis, and wherein a first distance (l 1) between the rotational axis and the cross-sectional contour at a first position is longer than a second distance (l 2) between the rotational axis and the cross-sectional contour at a second position, the second position being positioned farther from the opening than the first position is. at least one blade; a hub to which the at least one blade is mounted rotatably; and a spinner disposed so as to cover the hub, wherein the spinner includes a tubular part which extends around a rotational axis of the hub and which has an opening through which the blade extends, wherein the tubular part of the spinner has a shape such that, when an intersection of the tubular part and a virtual cylinder surrounding the opening and extending along a blade root of the blade is projected on a plane including an axis of the blade and the rotational axis, a projection line (32, 32', 32") of the intersection is within a range defined by a reference line connecting opposite ends (40, 42) of the projection line (32, 32', 32") and a reference curve (34, 34', 34") which is an intersection line, projected on the plane, of the virtual cylinder and a locus (21a, 21b) of the reference line rotating about the rotational axis, wherein the tubular part has a bulge at least around the opening, the bulge bulging outward from the locus (21a, 21b) in at least one part of a central region between the opposite ends (40, 42) of the projection line (32, 32' 32") with respect to a direction of the rotational axis of the hub, wherein the tubular part has a cross-sectional contour along a plane orthogonal to the rotational axis of the hub, in the at least one part of the central region, the cross-sectional contour having a distance from the rotational axis which varies in the circumferential direction of the rotational axis, and wherein a first distance (l 1) between the rotational axis and the cross-sectional contour at a first position is longer than a second distance (l 2) between the rotational axis and the cross-sectional contour at a second position, the second position being positioned farther from the opening than the first position is.