[Problem]The present invention provides a compound which is useful as an active ingredient of a pharmaceutical composition, in particular, a pharmaceutical composition for preventing and/or treating VAP-1-related diseases.[Means for Solution]The present inventors have conducted intensive studies on a compound having a VAP-1 inhibitory activity, and as a result, they have found that the compound or a salt thereof of the present invention exhibits an excellent VAP-1 inhibitory activity and is useful for preventing and/or treating VAP-1-related diseases, in particular, diabetic nephropathy or diabetic macular edema, thereby completing the present invention. In addition, the present invention relates to a pharmaceutical composition, in particular, a pharmaceutical composition for preventing and/or treating VAP-1-related diseases, which comprises the compound or a salt thereof of the present invention, and an excipient.