A lubricant supply device including a solid lubricant, a lubricant supply roller, a detector, and a varying device is provided. The lubricant supply roller is adapted to supply the lubricant to a toner image bearing member and is rotatable in a predetermined direction while slidably contacting both the solid lubricant and the toner image bearing member. The detector is adapted to detect an absolute humidity around the lubricant supply device. The varying device is adapted to vary an amount of the lubricant to be supplied to the toner image bearing member based on the absolute humidity detected by the detector.