To provide waste water treatment equipment which is capable of making efficiently treatment of organic waste water, reducing a running cost and equipment cost and reducing the amount of the sludge to be generated as a whole or making the material zero.

This waste water treatment equipment is provided with a biological treating vessel which is packed with biological carriers for aerobically and biologically treating the organic matter in the organic waste water, a sludge separating means which separates the solid from a liquid mixture composed of the sludge after the biological treatment and the treated water, a circulating flow passage which circulates part of the separated sludge to the biological treating vessel, a sludge treating vessel which aerobically and biologically treats the remaining separated sludge under higher temperature conditions than those of the biological treating vessel and a high-temperature sludge circulating flow passage which circulates the sludge after the high-temperature biological treatment to the biological treating vessel.