To provide a reagent applying device and a reagent applying method for electrophoresis analysis which make it possible to apply a reagent with a simple configuration at low cost. A reagent supplying device for supplying a reagent to the surface of a gel in electrophoresis analysis includes a reagent applying tool which is a plate-shaped body. The reagent applying tool includes at least one reagent holding section which penetrates the reagent applying tool in a thickness direction and which holds a reagent by capillary action, and a reagent spreading section for spreading, on the surface of the gel, a reagent supplied from a lower-side opening of the reagent holding section when the reagent applying tool is placed on the gel.