  Exploiting the sample of 30 local star-forming, undisturbed late-type
galaxies in different environments drawn from the GAs Stripping Phenomena in
galaxies with MUSE (GASP), we investigate the spatially resolved Star Formation
Rate-Mass ({\Sigma}SFR-{\Sigma}_star) relation. Our analysis includes also the
galaxy outskirts (up to >4 effective radii, re), a regime poorly explored by
other Integral Field Spectrograph surveys. Our observational strategy allows us
to detect H{\alpha} out to more than 2.7re for 75% of the sample. Considering
all galaxies together, the correlation between the {\Sigma}SFR and
{\Sigma}_star is quite broad, with a scatter of 0.3 dex. It gets steeper and
shifts to higher {\Sigma}_star values when external spaxels are excluded and
moving from less to more massive galaxies. The broadness of the overall
relation suggests galaxy-by-galaxy variations. Indeed, each object is
characterized by a distinct {\Sigma}SFR-{\Sigma}_star relation and in some
cases the correlation is very loose. The scatter of the relation mainly arises
from the existence of bright off-center star-forming knots whose
{\Sigma}SFR-{\Sigma}_star relation is systematically broader than that of the
diffuse component. The {\Sigma}SFR-{\Sigma}tot gas (total gas surface density)
relation is as broad as the {\Sigma}SFR-{\Sigma}_star relation, indicating that
the surface gas density is not a primary driver of the relation. Even though a
large galaxy-by-galaxy variation exists, mean {\Sigma}SFR and {\Sigma}_star
values vary of at most 0.7 dex across galaxies. We investigate the relationship
between the local and global SFR-M_star relation, finding that the latter is
driven by the existence of the size-mass relation.
