The invention belongs to the technical field of shaft couplers, and specifically discloses an adjustable shaft coupler. The adjustable shaft coupler comprises a main body, adjusting parts, shaft coupling keys, a shaft sleeve, fastening bolts and locking parts, wherein the main body is of a circular ring structure, the right end of the main body is equipped with a ring-shaped cavity, and the left end of the main body is equipped with a plurality of threaded holes I in the peripheral direction; the quantity of the adjusting parts is the same with that of the threaded holes I; the adjusting partsare fixedly arranged on the shaft coupler main body through the threaded holes I; the quantity of the shaft coupling keys is the same with that of the adjusting parts; the shaft coupling keys are fixedly arranged in the main body through the adjusting parts; the shaft coupling keys are connected with an output shaft; the shaft sleeve is positioned in the ring-shaped cavity; threaded holes II andkey slots are formed in the shaft sleeve; the fastening bolts are fixedly arranged on the shaft sleeve through the threaded holes II; the fastening bolts are used for fixing an input shaft which is arranged in the shaft sleeve in a penetrating mode; and the locking parts are fixedly arranged on the inner wall of the ring-shaped cavity in the peripheral direction for driving the main body to rotate.