An oxidation catalyst device is provided with a duct, a fan, a heater, an oxidation catalyst carrying element, and a heat-radiating duct. The duct is connected to a fixation device of the wet-type electrophotographic image forming apparatus. The fan, the heater and the oxidation catalyst carrying element are provided in the duct. The heat-radiating duct is installed to surround the duct and an airflow passage is formed between the outer wall of the duct and the inner wall of the heat-radiating d...