In this paper, we investigated the electrical properties of triisopropylsilyl (TIPS) pentacene organic thin-film transistor (OTFT) depending on solvent type. We spin coated TIPS pentacene by using chlorobenzene, p-xylene, chloroform, and toluene as solvents. Fabricated OTFT with chlorobenzene shows field-effect mobility of $1.0{ imes}10^{-2}cm^2/V{cdot}s$, on/off ratio of $4.3{ imes}10^3$ and threshold voltage of 5.5 V. In contrast, with chloroform, the mobility is $5.8{ imes}10^{-7}cm^2/V{cdot}s$, on/off ratio of $1.1{ imes}10^2$ and threshold voltage of 1.7 V. Moreover we measured the grain size of each TIPS pentacene solvent by atomic force microscopy (AFM). From these results, it can be concluded that a solvent with higher boiling point results in better electrical characteristics due to large grain size and high crystallinity of TIPS pentacene layer. In this paper TIPS pentacene with chlorobenzene shows the best electrical properties.