A sheet electric resistance measuring instrument (10, 11, 12, 13) comprising: first (20, 320) and second (22, 322) housings that are paired with each other and that sandwich a sheet from both sides of the sheet; a pair of electrodes that are provided on the first housing (20, 320) and that measure an electric resistance of the sheet sandwiched between the pair of electrodes and the second housing (22, 322); and a contact member (150, 155, 250) that is disposed between the pair of electrodes on the first housing (20, 320) and that is brought into contact with the sheet, the sheet electric resistance measuring instrument (10, 11, 12, 13) being characterized in that: - the contact member is formed of an elastic body or is attached to the first housing (20, 320) with an elastic body interposed between the contact member and the first housing (20, 320) and projects toward the second housing (22, 322) further than the electrodes do before the contact member is brought into contact with the sheet; - the contact member projects toward the second housing further than the electrodes do, and the second housing has a recess formed at a position that corresponds to the contact member; or in that - the sheet electric resistance measuring instrument further comprises an isolation mechanism that isolates the contact member from the sheet while an electric resistance is measured by the electrodes. first (20, 320) and second (22, 322) housings that are paired with each other and that sandwich a sheet from both sides of the sheet; a pair of electrodes that are provided on the first housing (20, 320) and that measure an electric resistance of the sheet sandwiched between the pair of electrodes and the second housing (22, 322); and a contact member (150, 155, 250) that is disposed between the pair of electrodes on the first housing (20, 320) and that is brought into contact with the sheet, the sheet electric resistance measuring instrument (10, 11, 12, 13) being characterized in that: - the contact member is formed of an elastic body or is attached to the first housing (20, 320) with an elastic body interposed between the contact member and the first housing (20, 320) and projects toward the second housing (22, 322) further than the electrodes do before the contact member is brought into contact with the sheet; - the contact member projects toward the second housing further than the electrodes do, and the second housing has a recess formed at a position that corresponds to the contact member; or in that - the sheet electric resistance measuring instrument further comprises - the contact member is formed of an elastic body or is attached to the first housing (20, 320) with an elastic body interposed between the contact member and the first housing (20, 320) and projects toward the second housing (22, 322) further than the electrodes do before the contact member is brought into contact with the sheet; - the contact member projects toward the second housing further than the electrodes do, and the second housing has a recess formed at a position that corresponds to the contact member; or in that - the sheet electric resistance measuring instrument further comprises an isolation mechanism that isolates the contact member from the sheet while an electric resistance is measured by the electrodes.