The present disclosure relates to a rotary engine having a crankshaft with an improved structure, the rotary engine including a housing, a rotor, housing covers, and a crankshaft installed to penetrate through the rotor so as to receive rotational force from the rotor, wherein the crankshaft includes a first member extending in one direction and having an insertion groove recessed in one side surface thereof, a second member extending to penetrate through a center portion of the housing and provided with a protruding portion on one end thereof to be fixedly inserted into the insertion groove, and a coupling member interposed at a position where the insertion groove and the protruding portion overlap each other such that the first member and the second member are closely coupled to each other.