An extrusion coating method of extruding a coating solution from a coater onto a web-shaped substrate, comprising steps of: conveying the substrate in a conveying direction; supporting by coming in contact with a first side surface of the substrate by a back-roll; and extruding simultaneously at least a lowermost layer solution and an adjacent layer solution onto a second side surface of the supported substrate in such a way that the lower most layer solution is coated on the second surface and the adjacent layer is superimposed on the lowermost layer solution, wherein a viscosity Va (Panulls) of the lowermost layer solution and a viscosity Vb (Panulls) of the adjacent layer solution satisfy the following formula:Vb/Vanull2.5.