A cloth for mattress including a knitted fabric that is knitted from blended yarns contains flame retardant rayon fibers, modacrylic fibers, polyimide fibers, and low-melting polyester fibers. The cloth for mattress can be obtained by producing blended yarns containing the flame retardant rayon fibers, the modacrylic fibers, the polyimide fibers, and the low-melting polyester fibers, and producing a knitted fabric by knitting the blended yarns. The cloth for mattress has excellent flame retardancy, ensures easy handling when used to cover a mattress, is resistant to pilling without reducing the strength of the blended yarns, and is also safe for contact with the human body.