The present invention provides an illumination device capable of improving an efficiency of acquiring light emitted by light emitting diodes, which are provided in a light source module and used as a light source, and capable of achieving a uniform luminance distribution, and provides a liquid crystal display device using the illumination device. The illumination device includes a circuit board, red, green and blue light emitting diodes, and a lens body. Each red, green and blue light emitting diode is mounted on the circuit board and connected with a wiring pattern formed on the circuit board. The lens covers the red, green and blue light emitting diodes, and includes first portions each having two first side surfaces and second portions each having two second side surfaces. The first and second portions are alternately arranged. A distance between the first side surfaces is larger than a distance between the second side surfaces. The three red, green and blue light emitting diodes are provided in each first portion of the lens.