PURPOSE: To provide a movable blade type oar constituted in such a way that the thrust of a blade can be used almost completely as the motive force of a boat and that the moving distance between the tip part and root part of the blade can be made almost the same.

CONSTITUTION: A rotary disc 2 is supported on a base 1, fixed to the oar mounting part of a boat vertically and parallelly with the proceeding direction of the boat, in such a way that the rotary shaft of the rotary disc 2 is vertical. An oar 3 has an oar shaft 3a, and an oar blade 3b rotatably fitted to the tip part or the oar shaft 38 through a shaft bar 4. A spherical joint part 3c is fitted to a fitting part 2a, provided at the center part of the rotary disc 2, in such a way that it can be put in spherical motion. A spherical joint part 5a formed on one end side of a connecting rod 5 of the specified length L is fitted to the fitting part 2b of the rotary disc 2, and a spherical joint part 5b formed on the other end side is fitted to a receiving member 7 fitted to the blade 3b. Both spherical joint parts 5a, 5b are fitted in such a state that they can be put in spherical motion.