Abstract: A core sphere or a wound-string core is held by a pair of bottom rollers and a pair of concave top rollers. Then, the bottom rollers are reciprocated in opposite directions respectively and rotated to rotate the core sphere or the wound-string core and wind rubber string, and a wound-string core of a predetermined diameter is obtained by pressurizing the core sphere or the wound-string core intermittently by the pair of top rollers with a predetermined pressure. Rotation frequency of the bottom roller is set to be 1100 rpm to 200 rpm, ratio of the rotation frequency of the bottom roller to number of the horizontal movement of the bottom roller is set to be 10:15 to 15:10, and ratio of pressurizing number of the top rollers to the number of the horizontal movement of the bottom roller is set to be 1:14 to 1:5.

Abstract: An apparatus for winding a string, made of rubber, on a core to form a wound string core. The apparatus is provided with plurality of string winding device, each of which is for winding a string on a core, a treatment device of string starting end which winds to fix a starting end of the string to the core, a treatment device of wound string end which fastens an end of the wound string core at the end of the winding process, and a core providing device for providing the core to the treatment device of string starting end.