An apparatus and a method of transmitting hierarchically modulated signals are provided. The present invention includes: a basic layer symbol generator generating a first layer signal; an enhancement layer symbol generator generating a second layer signal synchronized with the first layer signal and having different signal power; and a hierarchical modulator hierarchically modulating the first layer signal and the second layer signal, wherein the enhancement layer symbol generator performs constellation rotation rotating bundles configured as constellation points formed by the second layer signal based on constellation points of the first layer signal by a predetermined angle. According to the exemplary embodiment of the present invention, it is possible to improve the receiving performance of the second layer signals by applying the constellation rotation technology to the second layer signals in regards of the signal transmission system using the hierarchical modulation technology.