1. A processing device of which processing objects are categories contained in a hierarchical structure comprising categories into which products or services are classified and a keyword, comprising: an acquirer that acquires, for each category contained in the hierarchical structure, a frequency of the name of the category and the keyword co-occurring in a search query given to a search device; and an identifier that, when at least a part of the distribution of the acquired frequencies in the hierarchical structure is in conformity with at least one predetermined distribution pattern that is based on a sequence of frequencies within the hierarchical structure, identifies the position in the hierarchical structure of a category of which the name is given by the keyword based on the conformed part in the hierarchical structure and the position, in the sequence of frequencies occurring in the distribution pattern, pre-associated with the distribution pattern.