A signal processing device and method to accurately detect a distress signal from a search and rescue transponder and reduce a calculation load for the detection. The device may include an instantaneous frequency change rate calculating module configured to calculate a change rate of an instantaneous frequency of a complex reception signal generated from a reception wave received by a wave receiver, a memory configured to store a value obtained based on a reference frequency sweeping speed that is a frequency sweeping speed of the distress signal, and a distress signal determining module configured to determine whether the distress signal is issued from the search and rescue transponder, based on a comparison result between the instantaneous frequency change rate calculated by the instantaneous frequency change rate calculating module and the value obtained based on the reference frequency sweeping speed stored in the memory.