This paper presents solder paste rheology and its printability. Evaluating rheology of solder paste can help to solve problems in the fine pattern printing of solder paste. To quantify the solder paste rheology, viscosity, thixotropy index and viscosity restoration ratio were measured. For these measurements, six test samples of solder paste were prepared. These characteristics can be measured by changing shear rate of viscometer in several steps. Viscosity of solder paste lowers as shear rate increases. Low shear rate viscosity and high shear rate viscosity were calculated from viscosity and thixotropy indexes. These rheological characteristics are closely related to the printing quality. Printability of the solder pastes was evaluated by experimental procedure with a fine pitch QFP (Quad Flat Package) foot print test pattern. The Taguchi method was used in this printing experiment. Analysis of variance were performed to examine factors influencing printability. Evaluated items of printability were short deposit defect, bridge defect, line width increase ratio and rolling effect. Correlation analysis between rheological characteristics and printability of solder paste was performed. Results give a suggestive theoretical zone for good printing quality, that was figured out on the thixotropy index vs. viscosity plot. Its center point is 1800 [Poise] of viscosity and 0.6 of the thixotropy index. Evaluating rheology of solder paste is important when the printability of solder paste in fine pitch technology is concerned.