The present invention provides a device for enhancing fuel efficiency, the device including: a first casing in which first and second rotating pulverizers are disposed at both ends of a first injection hole at the center of the first casing and a fuel inlet is disposed on a first side of the first casing; a connection part which is disposed on a second side of the first casing and in which a second injection hole is formed in the center of the connection part; a second casing which is disposed on a second side of the connection part and in which a fuel outlet is disposed on a second, discharge hole side of the second casing; and a fuel guide means which is disposed inside the second casing and which includes first, second, third, and fourth guide tubes and first and second rotating guide tubes.