Provided are sodium hypochlorite pentahydrate crystals capable of long-term storage that have improved stability of sodium hypochlorite pentahydrate, which is effective as an oxidizing 5 agent or bactericide, in the vicinity of normal temperatures, and a method for producing the same. The sodium hypochlorite pentahydrate crystals are such that peaks appear at the locations of the angles of diffraction described in Table 1 of claim 1 over a range of 10°≤2θ (angle of diffraction)≤65° as measured by powder X-ray diffraction using a Cukα radiation source.