A high frequency transmitter-receiver which can prevent an antenna pattern from being broken. A radar apparatus is provided with a high frequency antenna, a base plate and a module. The antenna is comprised of an organic substrate and a metal pattern formed on the organic substrate. The high frequency antenna is adhered to the base plate astride the module. Here, the gap between the base plate and the module where the antenna is adhered is configured to satisfy the expression (an amount of change in gap size with respect to a change in use temperature)÷(an original gap size)≦6%.