Dilation of the external prepuce is a surgical operation for circumcision with narrowing of the prepuce. During the operation, the penile foreskin is disinfected with iodophor and then anesthetized with lidocaine aerosol or lidocaine injection for nerve block at the root of the penis to reduce the pain of the operation. After the anesthesia, a vascular clamp is inserted into the foreskin opening, the vascular clamp is opened, the outer foreskin opening is passively dilated, and the foreskin is attempted to be turned out.