To obtain a random pulse radar apparatus, in which spread spectrum radio waves containing a pseudorandom non-signal period are sued as an output signal, and in which reflected waves are received in the non-signal period to sharply reduce the peak electric power for transmitting.

A random pulse radar apparatus is composed of a transmitter which simultaneously uses two kinds of modulation a phase-shift keying part, which selects and outputs the phase of transmitted radio waves according to a pseudo noise digital code and time hopping to interrupt transmitting in a random manner according to the pseudo noise digital code to generate a hybrid spectrum spectrum signal; and a receiving device which delays and selectively detects reflected waves from an object due to the transmitted waves; an antenna device which is used for transmitting and receiving; to form one common or adjacent functional unit, and a reception control device which interrupts the operation of the receiving device during the time in which the transmitter outputs radio waves according to the modulation of time hopping. Then, the cross relation function between a transmitted signal and a received signal is computed, and the spatial distribution of the reflection intensity of the transmitted radio waves is measured.