Disclosed is a method and device for transmitting and receiving a signal by using modulation techniques in a wireless communication system. The method according to the present invention includes: selecting one of QAM and improved QAM according to at least one predefined criterion; encoding information bits to be transmitted according to a first encoding scheme and mapping encoded information bits to QAM symbols when the QAM is selected; encoding information bits to be transmitted according to a second encoding scheme and mapping encoded information bits to improved QAM symbols when the improved QAM is selected; and transmitting the QAM symbols or the improved QAM symbols through a given resource region.