Using XMM-Newton observation, we investigate properties of a flare from very active and poorly known star 47 Cas B. The luminosity at peak of the flare was found to be 4.77×10^30 erg/s, which is ~2 times more than that from a quiescent state. The quiescent state corona of 47 Cas was represented by two temperature plasma: 3.7 and 11.0 MK. The time-resolved X-ray spectroscopy of the flare showed a variable nature of temperature, emission measure and abundances. The
maximum temperature during the flare was found to be 72.8 MK. We inferred the size of a flaring loop using hydrodynamic loop model and the length was found to be of 3.3 × 10^10 cm. Using the RGS spectra, density during the flare was found to be 4.0 × 10^10 cm^(-3). The loop scaling laws were also applied in deriving physical parameters of the flaring plasma.