To facilitate the circuit construction and also to shorten the circuit construction time for a millimeter wave radio receiver by calculating the optimum receiving signal level based on the input circuit conditions and displaying the calculated signal level on the green zone of a receiving signal level monitor means.

When the transmitting/receiving circuit of a millimeter wave radio unit is constructed, the circuit distance and the circuit conditions such as the weather states like rainfall, etc., are inputted to a circuit condition input means 8. Based on these input circuit conditions, a data processing means 9 calculates the optimum receiving signal level and displays it as a green zone via a receiving level monitor means 6A that can set the green zone. Then the antenna direction is turned and adjusted until the index of the means 6A reaches the green zone. Thus it is possible to effectively adjust the antenna direction at the optimum point of the circuit conditions according to the ambient conditions such as the installing place of a radio receiver, e.g. the meteorological conditions such as rainfall, etc., as well as the circuit distance, etc., to be taken into consideration when a circuit is constructed.