Disclosed is a device for measuring the density of an image in regard to a liquid test patch. The device has: a fan for drying a test patch by blowing air to the test patch disposed on at least one of a photosensitive medium, a photosensitive belt and printing paper; a sensor for projecting infrared light to the dried test patch and measuring the density of the test patch based on the reflected light of the infrared light reflected from the test patch; and an adjustment unit for adjusting the mixing ratio of a toner and a carrier in accordance with the measured density. The device measures the amount of light reflected from the dried liquid test patch, thus allowing the density of the image to be measured accurately.