Abstract: The present invention relates to a flexible multi-functional logic circuit which switches a current direction to a serial or parallel direction using at least two single electron transistors (SETs) having the same pattern and as many field effect transistors (FETs) as the number of the single electron transistors and performs operations on multi-valued signals using Coulomb oscillation that is the unique characteristic of SET to enable conversion of a single logic circuit to four basic logic circuits of NAND, OR, NOR and AND gates and a device using the same.