  The isospin doublet scalar field with hypercharge 3/2 is introduced in some
new physics models such as tiny neutrino masses. Detecting the doubly charged
scalar bosons from the doublet field can be a good probe of such models.
However, their collider phenomenology has not been examined sufficiently. We
investigate collider signatures of the doubly and singly charged scalar bosons
at the LHC for the high-luminosity upgraded option (HL-LHC) by looking at
transverse mass distributions etc. With the appropriate kinematical cuts we
demonstrate the background reduction in the minimal model in the following two
cases depending on the mass of the scalar bosons. (1) The main decay mode of
the singly charged scalar bosons is the tau lepton and missing (as well as
charm and strange quarks). (2) That is into a top bottom pair. In the both
cases, we assume that the doubly charged scalar boson is heavier than the
singly charged ones. We conclude that the scalar doublet field with $Y = 3/2$
is expected to be detectable at the HL-LHC unless the mass is too large.
