To provide a portable water-purifying device which can simply and quickly purify quality of drinking water, which is handy to carry and which can be used with simplicity.

The portable water-purifying device for purifying quality of drinking water is constituted by accommodating a water permeable vessel 11 and active carbon 10 having drinking water purifying action in the vessel. The portable water-purifying device is directly cast in the drinking water and water purification effect of the drinking water is simply and quickly attained. Casting of the portable water-purifying device into water to be treated and withdrawal therefrom is performed with a tag at a top end of a picking thread.