A metal soap, including metal soap particles in which a fatty acid has from 6 to 22 carbons, and an inorganic crystal nucleating agent with an average particle size of 0.01 to 20 μm absorbed internally into the metal soap particles, wherein the cumulative diameter at 50% of the metal soap particles on a volumetric basis is 1.0 to 30.0 μm, and the internal absorption rate A, represented by formula (1) below, is 30% or greater. Internal absorption rate A=100−(X/X′)=100  Formula (1) X; amount of inorganic crystal nucleating agent contained within metal soap X′; amount of inorganic crystal nucleating agent contained within pulverized metal soap passed through a 325-mesh filter (wherein X and X′ are average values obtained by elemental analysis at three locations in an area of 15 μm square, using a scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDX).