Abstract: A coil bobbin for a current transformer is provided which requires no adhesive and no eyelets, as well as enables easy fixing of a primary coil to the coil bobbin without an increase in cost. The coil bobbin includes a configuration in which a coil bobbin 1 is formed, at an outer surface of one of flanges 4 thereof, with a primary coil mounting portion 7 and a primary coil fixing portion 8 so as to protrude outwardly. The primary coil mounting portion 7 and the primary coil fixing portion 8 are formed, at both sides thereof, with through holes 9, 9′ through which a pair of legs 3a of a primary coil 3 for detecting electric current extend. The primary coil fixing portion 8 is formed with a window 12 into which a jig is inserted. The window 12 is formed with concave fixing portions 12a.