To impart bactericidal properties to water treated with magnetic field, and to assist activity of oxygen by a constitution wherein a cup is formed by sealing hermetically inner and outer double walls, a cup and a lid member and magnet bodies are stored in the hollow part between the inside and the outside of the sealed cup to penetrate magnetism into a cup.

Permanent magnets 4 are disposed in a cavity 3 of a sealed cup 1 consisting of inner and outer double wall plates 1a and 1b made of a stainless steel and a lid member 5 is tightly stuck on the top of the sealed cup 1 by a screw, etc. As the permanent magnets 4 are arranged in the sealed cup 1, when a drink such as water, tea, juice, milk and liquor is put therein, iron content included in the drink is magnetized after approximately 10 min to become a magnetized drink. As the drink in the sealed cup 1 is thus magnetized by the power of the permanent magnet 4, and it becomes mild and tasty and active ions are generated in the magnetized drink, it is pref. that this beverage is drunk for 4-5 times for keeping daily health. This ionization phenomenon is effective to decrease in hypertension.