According to one exemplary embodiment of the present invention, there is provided an intake device of an internal combustion engine, having a plurality of intake passages for introducing an intake gas into a row of engine cylinders, respectively; and a secondary gas passage for introducing a secondary gas into the intake passages. The secondary gas passage includes a main gas channel, an adjacent gas channel extending downstream from the main gas channel adjacently and substantially in parallel with the main gas channel, and branch gas channels branching off from the adjacent gas channel and continuing to the intake passages.