The receiving device of the invention contains a correlational operation unit that executes a correlational operation between a first modulated signal having a spread-spectrum modulation applied and a first spread-spectrum signal string to output a correlational signal, and a decision circuit that decides an amplitude value of the correlational signal to output a decision signal. The decision circuit is composed of: a first detector that outputs a first detection signal when it detects that a value of the first correlational signal exceeds the first threshold, a second detector that outputs a second detection signal when it detects that the value of the first correlational signal exceeds the second threshold, and a detected signal selector that outputs the decision signal of a first value when the first detection signal is inputted, and outputs the decision signal of a second value when the second detection signal is inputted.