A sock formed by knitting along a knitting axis, the sock comprising: - a tubular leg part; - a tubular sole part; and - a heel part between the leg part and the sole part; the heel part comprising: - a plurality of mesh-number varying regions (V1, V2, V3, V4, V5, V6) arranged along the knitting axis; and the mesh-number varying regions (V1, V2, V3, V4, V5, V6) including: - an upper mesh-number varying region connected to a lower edge of the leg part; - a lower mesh-number varying region connected to an upper edge of the sole part; and - a plurality of intermediate mesh-number varying regions (V2, V3, V4, V5) between the upper mesh-number varying region and the lower mesh-number varying region, wherein the mesh-number varying regions (V1, V2, V3, V4, V5, V6) are constituted by mesh-number increasing regions (V1, V3, V5) and mesh-number reducing regions (V2, V4, V6) alternatingly arranged along the knitting axis, and wherein the number (CC1, CC2, CC3, CC4, CC5) of courses of tubular regions (C1, C2, C3, C4, C5) between mesh-number varying regions (V1, V2, V3, V4, V5, V6) is smaller than the number (CV1, CV2, CV3, CV4, CV5, CV6) of courses of the mesh-number varying regions (V1, V2, V3, V4, V5, V6), characterised in that a plurality of tubular regions (C1, C2, C3, C4, C5) is arranged between every two adjacent mesh-number varying regions (V1, V2, V3, V4, V5, V6), whereby the number of courses of the upper mesh-number varying region is smaller than the number of courses of the lower mesh-number varying region and the number of courses (CV2, CV3, CV4, CV5) of the intermediate mesh-number varying regions (V2, V3, V4, V5). - a tubular leg part; - a tubular sole part; and - a heel part between the leg part and the sole part; - a plurality of mesh-number varying regions (V1, V2, V3, V4, V5, V6) arranged along the knitting axis; and - an upper mesh-number varying region connected to a lower edge of the leg part; - a lower mesh-number varying region connected to an upper edge of the sole part; and - a plurality of intermediate mesh-number varying regions (V2, V3, V4, V5) between the upper mesh-number varying region and the lower mesh-number varying region, wherein the mesh-number varying regions (V1, V2, V3, V4, V5, V6) are constituted by mesh-number increasing regions (V1, V3, V5) and mesh-number reducing regions (V2, V4, V6) alternatingly arranged along the knitting axis, and wherein the number (CC1, CC2, CC3, CC4, CC5) of courses of tubular regions (C1, C2, C3, C4, C5) between mesh-number varying regions (V1, V2, V3, V4, V5, V6) is smaller than the number (CV1, CV2, CV3, CV4, CV5, CV6) of courses of the mesh-number varying regions (V1, V2, V3, V4, V5, V6), characterised in that a plurality of tubular regions (C1, C2, C3, C4, C5) is arranged between every two adjacent mesh-number varying regions (V1, V2, V3, V4, V5, V6), whereby the number of courses of the upper mesh-number varying region is smaller than the number of courses of the lower mesh-number varying region and the number of courses (CV2, CV3, CV4, CV5) of the intermediate mesh-number varying regions (V2, V3, V4, V5). wherein the mesh-number varying regions (V1, V2, V3, V4, V5, V6) are constituted by mesh-number increasing regions (V1, V3, V5) and mesh-number reducing regions (V2, V4, V6) alternatingly arranged along the knitting axis, and wherein the number (CC1, CC2, CC3, CC4, CC5) of courses of tubular regions (C1, C2, C3, C4, C5) between mesh-number varying regions (V1, V2, V3, V4, V5, V6) is smaller than the number (CV1, CV2, CV3, CV4, CV5, CV6) of courses of the mesh-number varying regions (V1, V2, V3, V4, V5, V6), characterised in that a plurality of tubular regions (C1, C2, C3, C4, C5) is arranged between every two adjacent mesh-number varying regions (V1, V2, V3, V4, V5, V6), whereby the number of courses of the upper mesh-number varying region is smaller than the number of courses of the lower mesh-number varying region and the number of courses (CV2, CV3, CV4, CV5) of the intermediate mesh-number varying regions (V2, V3, V4, V5).