To provide a thermocouple temperature detector mounting structure for a mixing tank for which the temperature detecting end of the thermocouple temperature detector mounted on the high viscosity mixing material mixer is capable of measuring temperature in real time and for which the mechanical load applied, by the flow of the material being mixed, on the temperature detecting end is made as small as possible. A temperature sensing portion (18) with a hemispherical tip, of a protective inner tube (17) that accommodates a thermocouple element (12) of a thermocouple temperature detector (10), is mounted on a mixing tank (1), for mixing a high viscosity mixing material, so as to project from the end of a protective tip (16) that projects into the mixing tank. With the outside diameter of a projecting base section (16a) of the protective tip that projects into the mixing tank being 2 to 3 times that of the protective inner tube, and with the projecting length (h) that projects into the mixing tank being the same length as the difference of the radius of the projecting base section of the protective tip and the radius of the protective inner tube, the outer circumferential face of a shoulder section (16b) of the protective tip, that is from the projecting base section of the protective tip to the site connecting to the outer circumference of the protective inner tube, is formed in a convex arcuate face that has a radius that is the difference of the radius of the projecting base section of the protective tip and the radius of the protective inner tube.