PROBLEM TO BE SOLVED: To provide a method for measuring the content of a powder resin in a resin fiber mat capable of easily measuring the content of the powder resin in a resin fiber mat made of a mixture of fiber and the powder resin.SOLUTION: The color density of a resin fiber mat 12 obtained by feeding a powder resin 2 mixed with a pigment 3 at a prescribed ratio and performing mixing is measured. The content of the powder resin 2 in the resin fiber mat 12 is obtained based on the relation between the content of the powder resin in the prescribed pigment mixing ratio of the resin fiber mat acquired beforehand and the color density thereof.