An abnormality diagnosis device is for an exhaust heat recovery equipment including an exhaust heat absorption part absorbing exhaust heat from an engine, a heat release part releasing at least part of the heat absorbed by the absorption part to engine coolant, a circulation loop passing through the absorption part and the release part, the medium circulating around the loop, and an opening and closing valve disposed in the loop between the absorption part and the release part. The equipment closes the valve to stop circulation of the medium when coolant temperature is a preset temperature or above. The device includes an abnormality determination device for determining whether the valve is in an abnormal opening state based on a heat amount transmitted from exhaust heat to coolant through the equipment, when coolant temperature is the preset temperature or above and thereby the valve is closed if the valve is normal.