To provide an operation method of an impact type pulverizer capable of treating both agglomerates needed to be pulverized and agglomerates no need to be pulverized by the same pulverizer.

The method is an operation method of an impact type pulverizer for pulverizing agglomerates by hit with a hammer rotating in a casing and repelling impact with a pulverizing plate, and when the agglomerates are pulverized, the gap between the hammer and the pulverizing plate and/or the rotation speed of the hammer is set to be a gap (preferably not wider than the maximum diameter of the agglomerates) proper to make the agglomerated have a prescribed particle diameter and when the agglomerates are not pulverized, the gap between the hammer and the pulverizing plate is set to be a gap (preferably at least 4 times as large as the maximum diameter of the agglomerates) proper not to pulverize the agglomerates.