The host finding behavior of Entobdella hippoglossi oncomiracidium, skin parasite of the Atlantic halibut was investigated. Almost of the parasite swam downward from the top to the bottom of the 150cm glass tube within 30 minutes. The average swimming speed of oncomiracidium was $0.32pm0.10cm/second$ throughout the experiment. When the parasites arrived on the bottom of the glass tube, they moved upwards and downwards continuously within the 10cm of the bottom. This behavior would suggest that it may be one of the essential methods for host searching of the parasite. When the oncomiracidia was exposed different stimuli, they responded positively light and halibut mucus.