A length measurement device comprising: a tape portion which is provided with a plurality of electrode pads (100a, 100b,..) arrayed along a longitudinal direction and is configured to be used in a state being wound around a measuring object; an impedance acquisition unit configured to select any pair of electrode pads from the plurality of electrode pads (100a, 100b,..) and acquire electrical impedance between the pair of electrode pads; a length calculation unit configured to calculate a length between the pair of electrode pads, based on a change in impedance of the pair of electrode pads; and a positional relationship data storage unit configured to store positional relationship data indicating a positional relationship between the plurality of electrode pads (100a, 100b,..), wherein the length calculation unit is configured to calculate the length between the pair of electrode pads, using the positional relationship data, wherein the impedance acquisition unit is configured to select a plurality of the pairs of electrode pads and acquire electrical impedance therebetween for each of the pairs of electrode pads, wherein the length calculation unit is configured to identify an area of the tape portion in which a pair of electrode pads having the electrical impedance set to be below a determination threshold (Zth) are arrayed, and calculates a length of the identified area, and wherein the impedance acquisition unit is further configured to perform a first acquiring step of selecting a plurality of pairs of electrode pads arrayed at a first separation distance and acquiring electrical impedance therebetween for each of the plurality of pairs of electrode pads, and a second acquiring step of selecting a plurality of pairs of electrode pads arrayed at a second separation distance larger than the first separation distance and acquiring electrical impedance therebetween for each of the plurality of pairs of electrode pads, the length measurement device being characterized in that in a case where a plurality of proximity areas (α) which are areas of the tape portion having the electrical impedance, acquired in the first acquiring step, set to be below the determination threshold exist with a non-proximity area (β) which is an area exceeding the determination threshold (Zth) interposed therebetween, the length calculation unit is configured to determine whether the electrical impedance acquired in the second acquiring step is below the determination threshold (Zth) in the non-proximity area (β), and calculates a length (ΔA') of an entire area in which the plurality of proximity areas (α) exist in a case where the electrical impedance is set to be below the determination threshold (Zth). a tape portion which is provided with a plurality of electrode pads (100a, 100b,..) arrayed along a longitudinal direction and is configured to be used in a state being wound around a measuring object; an impedance acquisition unit configured to select any pair of electrode pads from the plurality of electrode pads (100a, 100b,..) and acquire electrical impedance between the pair of electrode pads; a length calculation unit configured to calculate a length between the pair of electrode pads, based on a change in impedance of the pair of electrode pads; and a positional relationship data storage unit configured to store positional relationship data indicating a positional relationship between the plurality of electrode pads (100a, 100b,..), wherein the length calculation unit is configured to calculate the length between the pair of electrode pads, using the positional relationship data, wherein the impedance acquisition unit is configured to select a plurality of the pairs of electrode pads and acquire electrical impedance therebetween for each of the pairs of electrode pads, wherein the length calculation unit is configured to identify an area of the tape portion in which a pair of electrode pads having the electrical impedance set to be below a determination threshold (Zth) are arrayed, and calculates a length of the identified area, and wherein the impedance acquisition unit is further configured to perform a first acquiring step of selecting a plurality of pairs of electrode pads arrayed at a first separation distance and acquiring electrical impedance therebetween for each of the plurality of pairs of electrode pads, and a second acquiring step of selecting a plurality of pairs of electrode pads arrayed at a second separation distance larger than the first separation distance and acquiring electrical impedance therebetween for each of the plurality of pairs of electrode pads, the length measurement device being characterized in that in a case where a plurality of proximity areas (α) which are areas of the tape portion having the electrical impedance, acquired in the first acquiring step, set to be below the determination threshold exist with a non-proximity area (β) which is an area exceeding the determination threshold (Zth) interposed therebetween, the length calculation unit is configured to determine whether the electrical impedance acquired in the second acquiring step is below the determination threshold (Zth) in the non-proximity area (β), and calculates a length (ΔA') of an entire area in which the plurality of proximity areas (α) exist in a case where the electrical impedance is set to be below the determination threshold (Zth).