An analytic expression is obtained for the point-function demagnetization tensor of the uniformly magnetized equilateral triangular prism element. This result can be used to improve the precision in 3D finite element micromagnetic models, especially for complex boundary geometric shapes. The corresponding magnetometric demagnetization tensors and demagnetization factors are calculated with the expression. The demagnetization field is discussed at various aspect ratios with magnetization perpendicular to the triangle plane.