Provided is a muscle retractor for spine surgery including: first and second retractors having blades configured to support a spine and muscles, and insertion blocks extending from the blades and having facing open surfaces an expander having expansion arms slidably inserted into the insertion blocks of the first and second retractors, a gear rack movably installed at both of the expansion arms and having a gear section formed at one surface thereof, and a ratchet installed at the expansion arm moving along the gear rack and locked to or released from the gear section of the gear rack a slider accessibly inserted into the blade of the first retractor or the second retractor in a projected state and an auxiliary plate pivotally installed at a lower portion of the blade of the first retractor of the first and second retractors supporting the muscles.
