Provided is a computer that does not need quantum coherence or a cryogenic cooling device for a problem to be solved that needs an exhaustive search and a computing program thereof. Spin sj as a variable is caused to follow a local effective magnetic field Bj to introduce a system to a ground state of a problem-setting system. The ground state is a solution. At t=0, the magnetic field Bj is applied in the x-axis direction at all sites and all spins sj are initialized to the x-axis direction. With the lapse of time t, a magnetic field in the z-axis direction and interspin interaction are gradually applied, spin becomes +z-direction or −z-direction finally, and the z-component of spin sj becomes sjz=+1 or −1. When the direction spin sj is caused to follow the direction of the effective magnetic field Bj, a relaxation term to keep the direction of spin sj is introduced to improve convergence of a solution.