Provided are an antibacterial fiber in which the amount of incorporation of an antibacterial glass is made sufficient with a small amount by reducing the content of the antibacterial glass in a core portion compared to the content of the antibacterial glass in a sheath portion, and which could exhibit excellent antibacterial properties； and an efficient method for producing such an antibacterial fiber. Disclosed is an antibacterial fiber containing a thermoplastic resin and an antibacterial glass as mixing components, the antibacterial fiber having an average diameter adjusted to a value within the range of 1 to 50 µm, the antibacterial fiber including a core portion and a sheath portion, in which when a content of the antibacterial glass in the core portion is designated as Q1 (weight%) with respect to the total amount of the antibacterial fiber, and a content of the antibacterial glass in the sheath portion is designated as Q2 (weight%) with respect to the total amount of the antibacterial fiber, Q1 and Q2 satisfy the following relational expression (1):Q1<；Q2
