The present invention relates to an insulator as an insulating layer in a laminate which can inhibit dusting at the time of use, more particularly an electronic circuit component to which the insulator has been applied, particularly a wireless suspension. The insulator comprises a laminate of one or more insulation unit layers etchable by a wet process, the insulator having been subjected to plasma treatment after wet etching. The insulator exists mainly as an insulating layer in a laminate having a layer construction of first inorganic material layer-insulating layer-second inorganic material layer or a layer construction of inorganic material layer-insulating layer, and at least a part of the inorganic material layer has been removed to expose the insulating layer.