There is provided a fluidic device that is small, that can reduce contamination inclusion, and that can improve efficiency. A fluidic device includes a first constituent member internally having a first channel, and a mounting substrate internally having a second channel, the first constituent member being mounted on the mounting substrate. The mounting substrate has a storage portion for storing a fluid which is supplied to the first channel and a collecting portion for storing a fluid which is discharged from the first channel. The second channel has a supplying channel portion connected to the storage portion and a collecting channel portion connected to the collecting portion. The supplying channel portion and the collecting channel portion are connected to each other via the first channel.