Salted sea mustard (Undaria pinnatifida) was irradiated (0, 2,4 kGy) and stored for 6 months at $10{pm}1^{circ}C;and;30{pm}2^{circ}C$, respectively. Quality deterioration of stored salted sea mustard was observed to closely relate with the growth of halophilic bacteria and yeast. Gamma irradiation with 2 to 4 kGy doses reduced initial microbial loads of salted sea mustard by 1 to 2 log orders, but had little influence on the propagation during storage. Organoleptic characteristics of the sample showed no signifiant difference between nonirradiated control and irradiated samples during storage. Thus, gamma irradiation was little effective for improving the microbiological and organoleptic qualities of salted sea mustard associated with its storage stability.