Abstract: A logic device includes a ceramic superconducting element having magneto-resistive characteristics, and three electrodes provided adjacent the ceramic superconducting element, and constructed in such a manner that a current is applied to one of the three electrode so that a magnetic field greater than a threshold magnetic field is normally applied to the ceramic superconducting element, and the other electrodes are used for increasing and decreasing the magnetic field. A memory device includes a superconducting loop at least one portion thereof being formed by a ceramic superconducting element having grain boundaries, and an electrode provided in approximation to said ceramic superconducting element, whereby a current flowing through a portion of said superconducting loop which is other than said ceramic superconducting element can be captured in said superconducting loop by a control of a magnetic field generated by the current flowing through said electrode.