A developing blade (11) comprises a blade member (14) located along one side edge of a support member (12) and having a surface shape defined by a maximum height roughness Ry of 0.35 to 4.5 μm and a length ratio under load tp (at a 30% cut level) of 15% or less. Such a developing blade is manufactured by bringing a top mold (2) having a mold surface (2A) with a cavity (4) formed for the formation of a blade member and a gate (6) in communication with the cavity (4) in alignment with a bottom mold (3) having a flat mold surface (3A) such that at least a part of the support member (12) is positioned in the cavity (4), clamping together both the top and bottom molds, and pouring a molding material from the gate (6) to fill in the cavity (4).