Abstract: In a searching boat having a searching system for searching a spillage oil on the sea, the searching system comprises a driving device, an oil film appreciating device, and a radio transmitter. The driving device drives the searching boat in a predetermined direction on the spillage oil on the sea. The oil film appreciating device appreciates an edge of an oil film of the spillage oil to produce an oil edge appreciating signal. Supplied with the oil edge appreciating signal, the radio transmitter produces an arrival signal. The driving device may drive the searching boat in a forward direction as a forward mode driving when supplied with a start signal and may drive the searching boat in a backward direction opposite to the forward direction as a backward mode driving when supplied with the oil edge appreciating signal. Furthermore, the driving device may carry out the forward and the backward mode drivings every time when supplied with the oil edge appreciating signal.