The primary objective of this paper is to discuss the fundamental cooling characteristics of a magnetic heat pump, which operates based on an active magnetic regenerator (AMR) with a MnFeRuPSi compound as the magnetic refrigerant. This paper investigates the performance of an AMR made of flat parallel plates of a MnFeRuPSi compound. The basic components of the target system are a magnetic circuit, a test section, a fluid blowing system, and the associated instrumentation. The magnetic circuit, which consists of two opposing permanent magnets placed 20 mm apart and a yoke, is installed on a PC-controlled slider stage to change the magnetic field from 0 to 1.1 T with a reciprocating motion. The temperatures at both sides of the regenerator are measured and compared, along with the results for gadolinium. The results reveal that the MnFeRuPSi compound is a refrigerant candidate for a magnetic heat pump.