A sensor detects a detected value for a covered wire without metallic contact, and includes: a tubular support that has a male thread and an insertion channel in which the covered wire is inserted and supported; a tubular shell that is inserted into the support from a base end; a pillar-shaped detection electrode that is inserted in and supported by the shell; and a tubular threaded piece that screws onto the male thread, is rotatably attached onto the shell, and is moved, along the axis of the support, together with the shell and the detection electrode by a screwing operation. The detection electrode is configured so that the front surface is pressed onto the covered wire in the support when the detection electrode moves, resulting in the front surface becoming capacitively coupled to a core wire of the covered wire via an insulating covering.