•We purified the phlorotannins for the first time using chromatographic methods.•Purified phlorotannins contents and recovery were 905mg PGE/g and 92%.•We developed the process for an industrial-scale purification of phlorotannins. Phlorotannins are one of the most important bioactive polyphenols; however, their purification using chromatographic methods has not been explored. Here, we studied purification of phlorotannins from the crude phlorotannin extract (CPhE) of the brown seaweed Ecklonia cava using macroporous adsorption resins. For purification of phlorotannins, four resins (HP-20, SP-850, XAD-7HP, and XAD-2) were screened. Among them, HP-20 resin showed the highest adsorption and desorption capacities. In static adsorption tests, the adsorption capacity of HP-20 increased with increasing temperature (25–45°C). Optimal conditions for the dynamic experiments can be summarized as follows: total phlorotannin content (TPhC) in loading solution: 1.5mg PGE/mL, processing volume: 4 BV, flow rate: 1mL/min, temperature: 45°C, desorption solvent: 40% ethanol solution. After purification, TPhC (452mg PGE/g) and arsenic (180μg/g) of CPhE increased and decreased to 905mg PGE/g and 48μg/g, respectively. Recovery rate of phlorotannins from CPhE was 92%.