To provide a new nitrogen-containing heterocyclic compound or its salt, and to provide a pest control agent containing the compound as an active ingredient.

Provided are a nitrogen-containing heterocyclic compound represented by formula (I) (wherein, the dotted lines are each a single bond or a double bond, provided that one of the dotted lines is a single bond, and the other is a double bond) or its salt, and the pest control agent containing at least one of the nitrogen-containing heterocyclic compound and its salt as an active ingredient.