An inversion problem of integral operator in the form Sf =d^3/dx^3 Integral from 0 to w for S(x,t)f(t) dt under the condition that the kernel S(x, t) satisfies the equation (dx^3+dt^3)S(x, t) = 0 is investigated. It was proved that the operator A0S − SA*0 is finite if A0 = J3, where Jf = i integral from 0 to x for f(t) dx. Presentation for the inverse operatorT = S^−1 is obtained and it’s structure is studied.