  IRAS 19312+1950 is an SiO maser source that exhibits a prominent bipolar
nebulosity. Mapping observations of this object were made in the CO J=1--0,
13CO J=1--0, C18O J=1--0, CS J=2--1, and HCN J=1--0 lines and in the 150 GHz
continuum band. Near-infrared imaging observations were also made in the J, H,
and K-bands. The line profiles of the 12CO and HCN spectra consist of a weak
broad component with a line width of about 50 km/s and a strong narrow
component of the width of about 3 km/s. The profiles of the 13CO, C18O, and CS
lines have only the narrow component. Both of the components have an intensity
peak at the IRAS position. The narrow component was clearly resolved with a
15'' telescope beam. The spectral energy distribution of this object exhibits a
doubly peaked profile between 1 and 25 micron. The 150 GHz continuum flux
density was found to be 0.07 Jy, which is consistent with the flux density
predicted by the expanding envelope model with a mass loss rate of ~10^{-4}
M_sun/y at a distance of 2.5 kpc. We argue that the broad component originates
from the expanding envelope of this object, and that the hot dust cloud, which
is the source of the narrow component, is also physically associated with this
object. Though the present observations do not preclude the possibility of a
young stellar object, we argue that it is less plausible. We conclude that IRAS
19312+1950 is an AGB/post-AGB star that is evolved from a massive progenitor.
