Direct overwriting on a magnetic triple-layer magneto-optical disk has been performed by modulating the light intensity. Previously, direct overwriting had be performed only on a double-layer disk. The initializing field was reduced to 3.5 kOe for the triple-layer disk, compared with more than 5 kOe for a double-layer disk. A high C/N ratio of 50 dB was obtained for an overwritten bit length of 0.75 Am without any residual former signal. Margins of the light power for bits to be overwritten at an acceptable error rate are more than ±24 % for both the high and the low light intensity. The magnetic triple-layer disk is a promising medium for direct overwriting by light intensity modulation.