A silver-containing antimicrobial agent which is excellent in affinity to fiber, antimicrobial property, anti-fungus property and stability to heat and light. It comprises carboxymethyl cellulose containing silver in the amount of 0.01 to 1% by weight and having the degree of substitution to carboxymethyl group of not less than 0.4. The carboxymethyl cellulose may be a crosslinked compound to make the antimicrobial agent water resistant.