To provide a concrete structure of high durability without causing the corrosion of metals inside by preventing demineralized water such as rainwater from reaching the metals inside even if infiltrating through a clearance formed between the concrete structure and a cover forming member, which has no adverse effect on the formation of the concrete structure and the embedment of an embedded instrument.

An insert instrument 9 is formed by disposing an internal screw body 8 through a connecting ring 7 on the inner end side of a cylindrical sleeve 5 formed of an inorganic material and embedded in the concrete structure 4, and the outer peripheral surface of the sleeve 5 is provided with a water swelling agent layer 6. The water swelling agent layer 6 has high water absorptivity to the demineralized water such as rainwater and has low water absorptivity to an electrolytic water solution such as cement water.