A signal transfer method for transferring a multi-bit signal over a transfer path which is allocated to one bit includes the steps of: respectively assigning a plurality of parameters for a plurality of bits so that a value representing “0” or a value representing “1” is set to each of the plurality of parameters in accordance with a value of a corresponding one of the plurality of bits; outputting an electric signal to the transfer path, the electric signal expressing a combination of the plurality of parameters having the values as set in the assigning step; receiving the electric signal from the transfer path and extracting the plurality of parameters from the electric signal; and detecting the respective values of the plurality of parameters.