A viscometer comprising: a first stage having a first surface ; a second stage having a second surface and configured to rotate the second surface with the second surface being opposed and in proximity to the first surface ; a motor including a motor body and a shaft that is an output shaft of the motor body and is directly or indirectly connected to the second stage to rotate synchronously with the second stage ; a fixed member arranged to rotatably support the shaft and the motor body ; a strain gauge unit fixed to the fixed member and configured to be biased by a contact of the motor body when the motor body rotates in a first direction with respect to the fixed member ; a controller configured to control an operation of the motor and obtain viscosity in accordance with an output voltage from the strain gauge unit ; a casing provided to support the fixed member and house the controller ; the viscometer characterized in that it further comprises a cap removably attached to the fixed member to cover the second surface in an attached state and cause the second surface to be exposed in a removed state, wherein the viscometer further comprises: a rotation plate with a disk shape which is coaxially fixed to a tip of the shaft and is provided with a plurality of plate magnets fitted along a circumferential edge of the rotation plate ; a thrust bearing which is coaxially attached to the second stage in middle of a lower surface of the second stage ; and a plurality of stage magnets which are fitted to the lower surface of the second stage to surround the thrust bearing . a first stage having a first surface ; a second stage having a second surface and configured to rotate the second surface with the second surface being opposed and in proximity to the first surface ; a motor including a motor body and a shaft that is an output shaft of the motor body and is directly or indirectly connected to the second stage to rotate synchronously with the second stage ; a fixed member arranged to rotatably support the shaft and the motor body ; a strain gauge unit fixed to the fixed member and configured to be biased by a contact of the motor body when the motor body rotates in a first direction with respect to the fixed member ; a controller configured to control an operation of the motor and obtain viscosity in accordance with an output voltage from the strain gauge unit ; a casing provided to support the fixed member and house the controller ; the viscometer characterized in that it further comprises a cap removably attached to the fixed member to cover the second surface in an attached state and cause the second surface to be exposed in a removed state, wherein the viscometer further comprises: a rotation plate with a disk shape which is coaxially fixed to a tip of the shaft and is provided with a plurality of plate magnets fitted along a circumferential edge of the rotation plate ; a thrust bearing which is coaxially attached to the second stage in middle of a lower surface of the second stage ; and a plurality of stage magnets which are fitted to the lower surface of the second stage to surround the thrust bearing . a rotation plate with a disk shape which is coaxially fixed to a tip of the shaft and is provided with a plurality of plate magnets fitted along a circumferential edge of the rotation plate ; a thrust bearing which is coaxially attached to the second stage in middle of a lower surface of the second stage ; and a plurality of stage magnets which are fitted to the lower surface of the second stage to surround the thrust bearing . <EOS>