Disclosed is a detachment and displacement protection structure for insertion of flexible circuit flat cable. An inserter positioning section is formed on a flexible circuit flat cable and coupled with an inserter, which includes a metal member and a plastic member. In assembling, the plastic member is first positioned on a first surface of the inserter positioning section of the flexible circuit flat cable, and then the metal member is fit over the plastic member. A detachment and displacement protection structure is provided on the inserter positioning section to constrain the inserter from displacing and detaching in a flat cable extension direction due to being acted upon by an external force when the inserter is positioned on the inserter positioning section.