From Fukushima nuclear disaster, as the water which is supplied by rain and groundwater flow into reactor building, contaminated water which contains radioactive nuclides is occurred. Although about 600 tons of contaminated water was generated at the early of accident, as the groundwater management system is developing, about 150 tons of contaminated water is generated now. Tokyo Electric Power Holdings (TEPCO) operate a multi-nuclide removal equipment which is called ‘ALPS’ and store purified water (ALPS treated water) in the Fukushima NPP site by tank. From 2023, the Japanese government decided to dilute the stored ALPS treated water and discharge it into the ocean to secure space on the site. In this study, based on the data opened to the public by TEPCO, the current status of ALPS is investigated. The dilution and discharge process under conceptual design was investigated. In addition, the treatment capacity of ALPS was analyzed based on the radioactivity concentration data of 7 nuclides. And then, two points to be checked found. First, it was confirmed that the performance of ALPS temporarily decreased between 2015 and 2018 due to reduced replacement cycle of filter and absorbent. Second, it was confirmed that the ALPS treated water from specific ALPS still haven’t satisfied the discharge limit for I-129, Sr-90, and Cs-137. In the case of Cs-137, about 1.7 times the radioactivity concentration was detected compared to the discharge limit. For I-129 and Sr-90, about 2.4 times and 2.1 times of radioactivity concentration was detected compared to the discharge limit. From this study, some of the ALPS treated water are confirmed that the radioactivity concentration exceeds the discharge limit, and the treatment capacity of ALPS might be unstable depend on the ALPS operation such as replacement cycle. Therefore, before the discharging of contaminated water on 2023, it is necessary to inspect ALPS if it purifies contaminated water with reliability or not, and to secure the reliable evaluation method to measure radioactivity concentration.