A method of obtaining a shear rate occurring in a liquid sample for a tuning fork vibration type viscometer, in which a pair of vibrators are dunked in the sample liquid and vibrated by an electromagnetic drive equipped with a coil, a driving current is applied to the coil so as to set an amplitude of the vibrators within a predetermined amplitude value, and a viscosity of the sample liquid is calculated by measuring the driving current, such pair of vibrators each comprises a thin plate of which a leading end is provided with a rounded limb portion, such limb portions constituting a wet part to be contacted with the sample liquid and the other leading end are fixed to plate springs, such plate springs having a thinnest part acting as a fulcrum of the vibrator, the method comprising: a step of calculating the viscosity of the sample liquid by a measurement described above or input; a step of calculating a driving force on a center of the wet part of the vibrator from the driving current; and a step of calculating a shear stress exerted on the sample liquid from the driving force and a liquid contact area of the vibrator, wherein the shear rate is calculated from a ratio between the shear stress and the viscosity, characterized in that, the calculation of the driving force on the center of the wet part of the vibrator in the step of calculating the driving force comprises: a first step of calculating a power generated in the electromagnetic drive from a product of a density of magnetic flux, a driving current and a length of the coil of the electromagnetic drive; and a second step of dividing the power generated in the electromagnetic drive by a ratio between the distance to the center of the electromagnetic drive from the center of the thinnest part of the plate spring and the distance to the center of the wet area of the vibrator from the center of the thinnest part of the plate spring. a step of calculating the viscosity of the sample liquid by a measurement described above or input; a step of calculating a driving force on a center of the wet part of the vibrator from the driving current; and a step of calculating a shear stress exerted on the sample liquid from the driving force and a liquid contact area of the vibrator, wherein the shear rate is calculated from a ratio between the shear stress and the viscosity, characterized in that, the calculation of the driving force on the center of the wet part of the vibrator in the step of calculating the driving force comprises: a first step of calculating a power generated in the electromagnetic drive from a product of a density of magnetic flux, a driving current and a length of the coil of the electromagnetic drive; and a second step of dividing the power generated in the electromagnetic drive by a ratio between the distance to the center of the electromagnetic drive from the center of the thinnest part of the plate spring and the distance to the center of the wet area of the vibrator from the center of the thinnest part of the plate spring. a first step of calculating a power generated in the electromagnetic drive from a product of a density of magnetic flux, a driving current and a length of the coil of the electromagnetic drive; and a second step of dividing the power generated in the electromagnetic drive by a ratio between the distance to the center of the electromagnetic drive from the center of the thinnest part of the plate spring and the distance to the center of the wet area of the vibrator from the center of the thinnest part of the plate spring.