A surgical instrument (1) is provided with a rigid probe (2), and cuts off the trabecular meshwork by inserting this probe (2) into the canal of Schlemm. An inner tube portion having a cutter is equipped inside the probe, and the trabecular meshwork sucked in from a hole portion (22) is cut off by the cutter due to the movement of the inner tube portion. A protection portion (21) is formed on the tip the probe (2) and protects the outer wall of the canal of Schlemm when cutting the trabecular meshwork. According to the invention, an ophthalmic surgical instrument for glaucoma patients is provided, the surgical instrument having excellent operability and preventing cutting of parts that should not be cut off without fail.