Abstract: The present invention provides an angle changeable apparatus and an oar such that the shaft angle is easily adjustable. Disclosed is an angle changeable apparatus 1 for variably changing an angle of a shaft 110 inserted in a sleeve 10, including: a shaft-side member 20 fixed to the shaft 110; a sleeve-side member 30 fixed to the sleeve 10; and a slider 40 configured to slide between the shaft-side member 20 and the sleeve-side member 30, wherein the shaft-side member 20 has a first guiding part extending in a shaft direction, the sleeve-side member 30 has an elongated hole 31 extending in an oblique direction relative to the shaft direction, the slider 40 has a groove 41c guided by the first guiding part and a slider main body 41 guided by the elongated hole 31.