In a signal receiving circuit of a direct conversion system applied with a semiconductor integrated circuit for radio communication having a PLL requiring a clock signal, an LNA requiring low-noise receiving characteristics, and others, a variable coupling line is provided between clock signal buffers and at an input stage of the PLL, so that coupling between the variable coupling line and an input terminal of the LNA and coupling between the variable coupling line and a GND terminal of the LNA are made equal to each other at frequencies of higher harmonic waves of a clock signal. When the input terminal and the GND terminal of the LNA are excited at the same phase, since no output occurs at an output terminal of the LNA, an output of the LNA does not contain any higher harmonic wave of a clock signal.