A carbon nanotube assembly satisfies at least one of the following conditions (1) to (3): (1) an FT-IR spectrum of a CNT dispersion obtained by dispersing the CNT assembly has a peak based on plasmon resonance of the CNTs in a wave number range of greater than 300 cm−1 and 2000 cm−1 or less; (2) the highest peak in a differential pore capacity distribution of the CNT assembly is located within a pore size range of more than 100 nm and less than 400 nm; and (3) a two-dimensional spatial frequency spectrum of an electronic micrographic image of the CNT assembly has at least one peak within a range of 1 μm−1 or more and 100 μm−1 or less.