  We present a novel Lyman alpha (Ly$\alpha$) radiative transfer code, SEURAT,
where line scatterings are solved adaptively with the resolution of the
smoothed particle hydrodynamics (SPH). The radiative transfer method
implemented in SEURAT is based on a Monte Carlo algorithm in which the
scattering and absorption by dust are also incorporated. We perform standard
test calculations to verify the validity of the code; (i) emergent spectra from
a static uniform sphere, (ii) emergent spectra from an expanding uniform
sphere, and (iii) escape fraction from a dusty slab. Thereby we demonstrate
that our code solves the Ly$\alpha$ radiative transfer with sufficient
accuracy. We emphasise that SEURAT can treat the transfer of Ly$\alpha$ photons
even in highly complex systems that have significantly inhomogeneous density
fields. The high adaptivity of SEURAT is desirable to solve the propagation of
Ly$\alpha$ photons in the interstellar medium of young star-forming galaxies
like Ly$\alpha$ emitters (LAEs). Thus, SEURAT provides a powerful tool to model
the emergent spectra of Ly$\alpha$ emission, which can be compared to the
observations of LAEs.
