A revolving apparatus for a construction machine, comprising: an upper revolving structure which is mounted on a lower traveling structure through a swing circle; a reduction device which is disposed at said upper revolving structure and decelerates and outputs input rotation; an electric motor which is arranged on said reduction device and inputs rotation of a motor shaft to said reduction device; and an output shaft which outputs the rotation of said motor shaft decelerated by said reduction device to said swing circle, and a wet braking device which gives braking force with respect to the rotation of said motor shaft is provided on an upper end side of said electric motor, characterized in that said wet braking device comprises: a brake case which is disposed on an upper end side of said electric motor and accommodates an upper end portion of said motor shaft therein; an adapter which is detachably disposed at said motor shaft in said brake case; a plurality of rotating side brake disks arranged on an outer peripheral side of said adapter in said brake case; a plurality of non-rotating side brake disks arranged on an inner peripheral side of said brake case in a state of alternately overlapping said respective rotating side brake disks; a brake piston which gives braking force to said motor shaft by using pushing force of a spring member to frictionally engage said rotating side brake disks and said non-rotating side brake disks with each other and releases braking with respect to said motor shaft against said spring member based on supply of a brake release pressure from the outside; and a lubricant oil supplied into said brake case, wherein a lubricant oil inlet port which is placed near said rotating side brake disks and said non-rotating side brake disks and through which said lubricant oil flows in is provided on a lower end side of said brake case, and a lubricant oil outlet port through which said lubricant oil flowing between said rotating side brake disks and said non-rotating side brake disks flows out is provided in an upper end portion of said brake case. an upper revolving structure which is mounted on a lower traveling structure through a swing circle; a reduction device which is disposed at said upper revolving structure and decelerates and outputs input rotation; an electric motor which is arranged on said reduction device and inputs rotation of a motor shaft to said reduction device; and an output shaft which outputs the rotation of said motor shaft decelerated by said reduction device to said swing circle, and a wet braking device which gives braking force with respect to the rotation of said motor shaft is provided on an upper end side of said electric motor, characterized in that said wet braking device comprises: a brake case which is disposed on an upper end side of said electric motor and accommodates an upper end portion of said motor shaft therein; an adapter which is detachably disposed at said motor shaft in said brake case; a plurality of rotating side brake disks arranged on an outer peripheral side of said adapter in said brake case; a plurality of non-rotating side brake disks arranged on an inner peripheral side of said brake case in a state of alternately overlapping said respective rotating side brake disks; a brake piston which gives braking force to said motor shaft by using pushing force of a spring member to frictionally engage said rotating side brake disks and said non-rotating side brake disks with each other and releases braking with respect to said motor shaft against said spring member based on supply of a brake release pressure from the outside; and a lubricant oil supplied into said brake case, wherein a lubricant oil inlet port which is placed near said rotating side brake disks and said non-rotating side brake disks and through which said lubricant oil flows in is provided on a lower end side of said brake case, and a lubricant oil outlet port through which said lubricant oil flowing between said rotating side brake disks and said non-rotating side brake disks flows out is provided in an upper end portion of said brake case.