A device for measuring an inclination of a green in a golf course. The device includes: a rotation member (200) having a weight member (210) provided eccentrically relative to a central axis of the rotation member such that the rotation member (200) freely rotates around a rotation shaft (220), the rotation member (200) having horizontal and vertical measurement lines; a first casing (110) having an accommodation space (112); and a second casing (120) fitted over the first casing (110), the second casing (120) having first rotation graduations, a horizontal judge line (h) and a vertical judge line (v), wherein the rotation member (200) comes into close contact with both the first casing (110) and the second casing (120), and then is stopped by a pressure generated between the first and second casings or by simultaneously pressing both a flange (224) of the rotation shaft and the first casing (110).