A titanium carbonitride-based cermet insert containing a titanium carbonitride-based cermet, which is a sintered body of a compact having a blended composition comprising, by mass%, at least: 20 to 30% of tungsten carbide; 5 to 10% of at least one of tantalum carbide and niobium carbide; 5 to 10% of Co; 5 to 10% of Ni; and 50 to 60% of titanium carbonitride, having a microstructure comprising 75 to 90 area% of a hard phase and the balance as a binding phase, wherein the hard phase comprises: a first hard phase having a core-having structure in which a core portion consists of a titanium carbonitride phase, and a peripheral portion consists of a complex carbonitride phase having Ti, W, and at least one of Ta and Nb (to be referred to as (Tl, W, Ta/Nb)CN); a second hard phase having a core-having structure in which both a core portion and a peripheral portion consist of (Ti, W, Ta/Nb)CN phases; and a third hard phase having a single phase structure consisting of a titanium carbonitride phase, and the binding phase consists of a W-Co-Ni-based alloy having a composition comprising, as a ratio in the binding phase and by mass%, at least: 18 to 33 mass% of Co; 20 to 35 mass% of Ni; and Ti and at least one of Ta and Nb, the total amount thereof is 5 mass% or less; or which is a sintered body of a compact having a blended composition comprising, by mass%, at least: 20 to 30% of tungsten carbide; 5 to 10% of at least one of tantalum carbide and niobium carbide; 1 to 5% of at least one of zirconium carbide, vanadium carbide and molybdenum carbide; 5 to 10% of Co; 5 to 10% of Ni; and 50 to 60% of titanium carbonitride, having a microstructure comprising 75 to 93 area% of a hard phase and the balance as a binding phase, wherein the hard phase comprises: a first hard phase having a core-having structure in which a core portion consists of a titanium carbonitride phase, and a peripheral portion consists of a complex carbonitride phase having Ti, W, at least one of Ta and Nb, and at least one of Zr, V and Mo (to be referred to as (Ti, W, Ta/Nb, Zr/V/Mo)CN); a second hard phase having a core-having structure In which both a core portion and a peripheral portion consist of (Ti, W, Ta/Nb, Zr/V/Mo)CN phases; and a third hard phase having a single phase structure consisting of a titanium carbonitride phase, and the binding phase consists of a W-Co-Ni-based alloy having a composition comprising, as a ratio in the binding phase and by mass%, at least: 18 to 33 mass% of Co; 20 to 35 mass% of Ni; and Ti, at least one of Ta and Nb, and at least one of Zr, V and Mo, the total amount thereof is 5 mass% or less; and which is characterized in that the binding phase comprises 40 to 60 mass% of W. 20 to 30% of tungsten carbide; 5 to 10% of at least one of tantalum carbide and niobium carbide; 5 to 10% of Co; 5 to 10% of Ni; and 50 to 60% of titanium carbonitride, a first hard phase having a core-having structure in which a core portion consists of a titanium carbonitride phase, and a peripheral portion consists of a complex carbonitride phase having Ti, W, and at least one of Ta and Nb (to be referred to as (Tl, W, Ta/Nb)CN); a second hard phase having a core-having structure in which both a core portion and a peripheral portion consist of (Ti, W, Ta/Nb)CN phases; and a third hard phase having a single phase structure consisting of a titanium carbonitride phase, and the binding phase consists of a W-Co-Ni-based alloy having a composition comprising, as a ratio in the binding phase and by mass%, at least: 18 to 33 mass% of Co; 20 to 35 mass% of Ni; and 18 to 33 mass% of Co; 20 to 35 mass% of Ni; and 20 to 30% of tungsten carbide; 5 to 10% of at least one of tantalum carbide and niobium carbide; 1 to 5% of at least one of zirconium carbide, vanadium carbide and molybdenum carbide; 5 to 10% of Co; 5 to 10% of Ni; and 50 to 60% of titanium carbonitride, a first hard phase having a core-having structure in which a core portion consists of a titanium carbonitride phase, and a peripheral portion consists of a complex carbonitride phase having Ti, W, at least one of Ta and Nb, and at least one of Zr, V and Mo (to be referred to as (Ti, W, Ta/Nb, Zr/V/Mo)CN); a second hard phase having a core-having structure In which both a core portion and a peripheral portion consist of (Ti, W, Ta/Nb, Zr/V/Mo)CN phases; and a third hard phase having a single phase structure consisting of a titanium carbonitride phase, and 18 to 33 mass% of Co; 20 to 35 mass% of Ni; and