A multilevel signal transmitting apparatus transmits a multilevel data signal with M voltage levels, and a multilevel clock signal with (M−2) voltage levels, to a multilevel signal receiving apparatus, where M is an even number equal to or more than four. The voltage levels of the multilevel data signal include M/2 first voltage levels larger than a reference voltage level, and M/2 second voltage levels smaller than the reference voltage level. Between each pair of adjacent voltage levels among the first voltage levels, one voltage level of the multilevel clock signal is set. Between each pair of adjacent voltage levels among the second voltage levels, one voltage level of the multilevel clock signal is set. An average of the voltage levels of the multilevel clock signal has a value between a minimum of the first voltage levels, and a maximum of the second voltage levels.