To provide an in-vehicle signal processing device that generates a broadcast signal by processing an input signal, transmits the broadcast signal from a transmitting antenna toward an in-vehicle antenna, and transmits the broadcast signal from the transmitting antenna even when a failure occurs in the input signal.

The in-vehicle signal processing device includes a re-transmitter 30 which selects and demodulates a digital television broadcast of a specific broadcast channel on the basis of a signal received from a signal receiving antenna 3, generates an analog television broadcast signal of a channel for re-transmission on the basis of the demodulated signal, and again transmits the generated signal from an antenna 41. The re-transmitter 30 is provided, in addition to a channel-selection/demodulation circuit 36, with a test signal generation circuit 39 for generating a test signal. A control circuit 38, according to a switch signal input from a remote transmitter 8, switches whether to generate the analog television broadcast signal based on the signal demodulated by the channel-selection/demodulation circuit 36 or to generate the analog television broadcast signal based on a test signal.