A carrier includes attachment holes to which a catalyst attaches, and non-attachment holes to which the catalyst does not attach. An attachment quantity measurement device includes an electromagnetic wave output device that outputs a terahertz wave toward the carrier, an electromagnetic wave detector that detects the terahertz wave which has transmitted through the carrier, a reference value obtainer that obtains, based on a result detected by the electromagnetic wave detector, any one of an absorption rate, a group delay, and a dispersion of the terahertz wave in the non-attachment holes, and an attachment quantity obtainer that obtains, based on the result detected by the electromagnetic wave detector and the result obtained by the reference value obtainer, a weight or a density of the catalyst present in the attachment holes.