  A few years ago N.A'Campo invented a construction of a link from a real curve
immersed into a disk. In the case of the curve originating from the real
morsification method the link is isotopic to the link of the corresponding
singularity. There are some curves which do not occur in the singularity
theory. In this article we describe the Casson invariant of A'Campo's knots as
a J^{+/-}-type invariant of the immersed curves. Thus we get an integral
generalization of the Gusein-Zade--Natanzon theorem which says that the Arf
invariant of a singularity is equal to J^{-}/2(mod 2) of the corresponding
immersed curve. It turns out that this invariant is a second order invariant of
the mixed J^{+}- and J^{-}-types.
