The magnetic treatment effects on mushroom spawn growth and yield were studied. The spawn of mushroom were exposed to full-wave rectified sinusoidal magnetic field. The spawn were grown after magnetic field treatment under controlled laboratory conditions. The magnetic field treatment resulted in significant increase (P<0.05) in the growth and yield of mushroom. The number of pin heads formed, number of pin heads developed into mature mushrooms, fresh (wet) and dry masses increased up to 38.18, 34.83, 76.43, and 38.26%, respectively, while reduction in number of days for spawn complete running and number of days for appearance of pin heads was found to be -3.14and -26.86%, respectively.