To make skill for an adjusting work unnecessary, simply and easily execute the adjusting work, and compose an instrumentation line of the number of devices half or less as much as the number of devices in the conventional instrumentation line so as to reduce the cost of an equipment by a method wherein the forward motions of a sleeve and of a cutter shaft are urged by a coiled spring.

In this automatically pressing type under-water cutting equipment, a piston 122 and a cylinder 133 are provided between a housing 110 and a sleeve 120 and, at the same time, a coiled spring for urging the sleeve 120 and a cutter shaft 130 forwards is provided, resulting in urging the sleeve 120 forwards with the coiled spring 140. Thus, by applying an air pressure on only one side of the piston 122, a predetermined pressing can be obtained.