As space development and exploration progress, the need for high-performance propulsion systems becomes increasingly crucial. Electric propulsion utilizing a strong magnetic field to enhance thrust performance emerges as a promising candidate. In this study, we propose a kilowatt-class plasma thruster incorporating a high-temperature superconducting magnet capable of generating a high magnetic field in the 1 T range. The thruster operates based on electrostatic ion acceleration, utilizing the potential difference across the magnetic field lines. To achieve high magnetic field strengths, the superconducting magnet is cooled by a cryocooler, enabling efficient power-saving operation up to a magnetic field strength of 0.8 T. During the experiment, it was observed that the ignitability of the thruster was compromised at high magnetic field strengths. However, through modification of the anode electrode shape, ignitability was improved. The experimental results demonstrate notable performance improvements with higher magnetic fields, culminating in a thrust efficiency of 26.5% with a specific impulse of 1930 s at 0.8 T. These findings underscore the potential of utilizing high-temperature superconducting magnets in plasma thrusters for achieving enhanced thrust performance. The successful development of this kilowatt-class plasma thruster represents a significant step towards realizing efficient propulsion systems for future space missions.