This study presents a rapid and cost-effective method for fabricating microchannels for rarefied gas flow applications using maskless photolithography. The geometrical characteristics of the microchannels were characterized via optical microscopy and profilometry, while their fluidic performances were characterized for gas flows at varying levels of rarefaction. The fluid conductance of the fabricated microchannels was measured and compared with theoretical predictions, demonstrating excellent agreement, thus confirming the precision of the fabrication process. Our findings indicate that the microchannels maintain dimensional integrity across different pressure levels, validating the reliability of the chosen materials and methods. Through this research, we have established a robust, low-cost, and rapid fabrication process based on maskless photolithography for producing affordable microfluidic devices for rarefied gas flow applications.