To provide a manufacturing method of a gasket, with which a gasket, which has high heat shock durability and, further, a narrow line width and is high, can be formed on a cover body under high compression.

A method of manufacturing a gasket, in which a gasket material is extruded from an extrusion port of a three-dimensional automatic coating control device to a cover body and the extruded gasket material is cured to integrate the cover body and the gasket, is characterized in that the gasket material is extruded from the extrusion port in such a manner that a ratio (h/w) between a height (h) of the gasket and a line width (w) of an adhering surface of the gasket to the cover body is 1.7 to 20 and a ratio (h/l) between the height (h) of the gasket and a width (l) of the gasket at an intermediate point in the height (h) of the gasket becomes 0.85 to 1.1.