The invention discloses a crankshaft machining device and a crankshaft machining method, and relates to the technical field of crankshaft machining. The crankshaft machining device comprises a crankshaft eccentric shaft sleeve component and an adjustable eccentric centre component, wherein the crankshaft eccentric shaft sleeve component comprises an eccentric shaft sleeve and a spline collet chuck; and the spline collet chuck is embedded to the eccentric shaft sleeve and is provided with a spline hole fixed to a crankshaft to be machined. The adjustable eccentric centre component comprises a rotary centre and a linear sliding rail component, wherein the rotary centre is glidingly arranged to the linear sliding rail component and comprises a centre matched with the crankshaft to be machined. The crankshaft machining device has the advantage of high positioning accuracy, can machine eccentric shaft sections at different phase angles, realizes rapid inserting and extracting, and improvesthe work efficiency.