  The studies of the complex molecular emission lines in millimeter and
submillimeter wavelengths towards the hot molecular cores demonstrate valuable
details about the chemical complexity in the interstellar medium (ISM). We
presented the first detection of the rotational emission lines of the complex
organic molecule methyl formate (CH$_{3}$OCHO) towards the hot molecular core
region IRAS 18566+0408 using the high-resolution Atacama Large
Millimeter/Submillimeter Array (ALMA) band 3 observation. The estimated column
density of CH$_{3}$OCHO using the rotational diagram analysis was
(4.1$\pm$0.1)$\times$10$^{15}$ cm$^{-2}$ with rotational temperature
102.8$\pm$1.2 K. The estimated fractional abundance of CH$_{3}$OCHO towards the
IRAS 18566+0408 relative to hydrogen (H$_{2}$) was 3.90$\times$10$^{-9}$. We
noted that the estimated fractional abundance of CH$_{3}$OCHO is fairly
consistent with the simulation value predicted by the three-phase warm-up model
from Garrod (2013). We also discussed the possible formation mechanism of
CH$_{3}$OCHO towards the hot molecular cores.
