To provide a metallic tone coating layer capable of expressing a specific feeling produced by the metal itself or a change of feeling with the passage of time, independent from a shape of a substrate, and reducing a harmful solvent as much as possible, its metallic tone sheet and a decorative sheet, and a method of forming a metallic tone coating layer.

A metallic tone coating layer is manufactured by coating and drying a surface treatment agent 5 containing 23±5 pts.wt. of a binding agent 3 mainly containing 40 to 55 wt.% of a varnish resin, 30 to 45 wt.% of butyl acetate, 1 to 10 wt.% of propylene glycol monomethyl ether acetate and 1 to 5 wt.% of xylene, and 2.4±0.4 pts.wt. of an activator 4 for activating the binding agent 3, relative to 100 pts.wt. of a metal fine powder 2, on a surface of a substrate 6, and making the content of a metal component in a coating surface treatment agent 5A at least 90 wt.% or more after the drying.