Provided is a technique whereby the measurement of a metal catalyst holding amount may be performed accurately. A holding amount measurement unit 50 irradiates an electromagnetic wave from an oscillator 52 onto a base material 90 being transported in the Y axis direction and detects the field intensity of the electromagnetic wave transmitted through the base material 90, thereby measuring the metal catalyst holding amount in a catalyst layer 92. The holding amount measurement unit 50 is equipped with: an edge position specification unit 6050 specifying the positions of edges 92E, 92E, on both sides in the Y axis direction of the catalyst layer 92; and a holding amount specification unit 604 eliminating, from the field intensity of electromagnetic waves detected by a plurality of detection elements 540, the intensity of diffracted electromagnetic waves arising from the diffraction of the electromagnetic waves at the positions of the edges, to specify the holding amount at each of the transmission positions in
