A fuel vapor processing apparatus includes a case defining therein a flow passage including an adsorption chamber, an adsorption material disposed in the adsorption chamber; and a density gradient filter disposed in the flow passage at a position on an upstream side of the adsorption material with respect to a direction of flow of purge air for desorbing fuel vapor from the adsorption material. The density gradient filter includes a first portion having a first density, a second portion having a second density, and a third portion having a third density. The third portion is positioned on a downstream side of the first portion with respect to the direction of flow of the purge air and the second portion is positioned between the first portion and the third portion. Each of the first density and the third density is higher than the second density.
