Provided is an organic semiconductor transistor including plural electrodes, and an organic semiconductor layer containing at least one fluorene compound represented by the following formula (I): wherein R1 represents an alkyl group having from 1 to 8 carbon atoms; R2 and R3 each independently represent an alkyl group having from 1 to 8 carbon atoms, or an alkoxy group having from 1 to 8 carbon atoms; and n represents an integer of from 1 to 3.