A signal transmission system comprising a transmission side including a modulation signal generating unit that generates a modulation signal using a Manchester code with a duty ratio of 50% in accordance with transmission data; and a receiving side including: a clock generating unit (6, 10, 20) that generates a clock having an amount of delay with respect to a rising edge or falling edge of the modulation signal generated by the modulation signal generating unit; and a data detecting unit that generates received data by carrying out sampling processing of the modulation signal generated by the modulation signal generating unit in synchronization with the clock generated by the clock generating unit (6, 10, 20), characterized in that when it is assumed that a period of the transmission data is T and the amount of delay in the clock generating unit (6, 10, 20) is not less than 0.5T and not greater than 1T, the modulation signal generating unit: outputs the Manchester code "1" with the duty ratio of 50% as a start signal; reads the transmission data; outputs the Manchester code "1" with the duty ratio of 50% if the transmission data read is "0"; outputs the Manchester code "0" with the duty ratio of 50% followed by the Manchester code "1" with the duty ratio of 50% if the transmission data read is "1"; and repeats an operation from reading to conversion of the transmission data until conversion and output of all the transmission data have been completed. a clock generating unit (6, 10, 20) that generates a clock having an amount of delay with respect to a rising edge or falling edge of the modulation signal generated by the modulation signal generating unit; and a data detecting unit that generates received data by carrying out sampling processing of the modulation signal generated by the modulation signal generating unit in synchronization with the clock generated by the clock generating unit (6, 10, 20), characterized in that when it is assumed that a period of the transmission data is T and the amount of delay in the clock generating unit (6, 10, 20) is not less than 0.5T and not greater than 1T, the modulation signal generating unit: outputs the Manchester code "1" with the duty ratio of 50% as a start signal; reads the transmission data; outputs the Manchester code "1" with the duty ratio of 50% if the transmission data read is "0"; outputs the Manchester code "0" with the duty ratio of 50% followed by the Manchester code "1" with the duty ratio of 50% if the transmission data read is "1"; and repeats an operation from reading to conversion of the transmission data until conversion and output of all the transmission data have been completed. outputs the Manchester code "1" with the duty ratio of 50% as a start signal; reads the transmission data; outputs the Manchester code "1" with the duty ratio of 50% if the transmission data read is "0"; outputs the Manchester code "0" with the duty ratio of 50% followed by the Manchester code "1" with the duty ratio of 50% if the transmission data read is "1"; and repeats an operation from reading to conversion of the transmission data until conversion and output of all the transmission data have been completed.