A coil assembly in which a slack can be formed in a coil wire without increasing assembly cost, and a stepping motor using the same, are provided; the coil assembly includes a bobbin 232 having flange portions 233 and 234 at both ends thereof, multiple terminal pin embedding portions 235a arranged at one flange portion 234, a terminal pin 236 embedded in the terminal pin embedding portion 235a, and a coil 231 of which an end portion of coil wire 237 is entwined around the terminal pin 236, the coil wire 237 wound around the bobbin 232, in which a concave portion 238 which concaves to a radial direction of the bobbin 232 and penetrates to an axial direction of the bobbin 232 is formed between the terminal pin embedding portions 235a, the coil wire 237 exists from a base portion of the terminal pin 236, passes through the concave portion 238, started to be wound around the bobbin 232, and has a slack portion 237a which exists in the concave portion 238.