A detection apparatus according to the present disclosure includes a signal output unit configured to output a measurement signal that includes a component having a first frequency to a transmission line, a signal measurement unit configured to measure a response signal, from the transmission line, to the measurement signal output from the signal output unit and a processing unit configured to generate a difference signal that is a difference between the response signal measured by the signal measurement unit and a reference signal that is based on the measurement signal, calculate an index value that indicates a strength of a correlation between the reference signal and the difference signal, and detect an abnormality in the transmission line on the basis of the calculated index value.