A hot-rolled steel sheet for coiled tubing, the steel sheet having a chemical composition containing, by mass%, C: 0.10% or more and 0.16% or less, Si: 0.1% or more and 0.5% or less, Mn: 0.8% or more and 1.8% or less, P: 0.001% or more and 0.020% or less, S: 0.0050% or less, Al: 0.01% or more and 0.08% or less, Cu: 0.1% or more and 0.5% or less, Ni: 0.1% or more and 0.5% or less, Cr: 0.5% or more and 0.8% or less, Mo: 0.10% or more and 0.5% or less, Nb: 0.01% or more and 0.05% or less, Ti: 0.01% or more and 0.03% or less, N: 0.001% or more and 0.006% or less, optionally one, two, or more selected from B: 0.0005% or more and 0.0050% or less, V: 0.01% or more and 0.10% or less, Ca: 0.0005% or more and 0.0100% or less, REM: 0.0005% or more and 0.0200% or less, Zr: 0.0005% or more and 0.0300% or less, and Mg: 0.0005% or more and 0.0100% or less, and a balance of Fe and inevitable impurities, a microstructure at a position located at 1/2 of a thickness of the steel sheet including bainite and bainitic ferrite in a total amount of 80% or more in terms of area fraction, in which an amount of solid solution Nb is 20% or more of a total Nb mass content, a yield strength of 480 MPa or more, a tensile strength of 600 MPa or more, a yield-strength difference (ΔYS) of 100 MPa or more, where the yield-strength difference is defined as a difference in yield strength between before and after a prestrain-heat treatment, in which the steel sheet is subjected to a heat treatment at a temperature of 650°C for 60 seconds after 5% pre-straining, and a yield strength of 620 MPa or more after the prestrain-heat treatment, wherein the yield strength and the tensile strength are obtained by performing a tensile test on a JIS No. 5 tensile test piece taken from the hot-rolled steel sheet so that the tensile direction is the L-direction. a chemical composition containing, by mass%, C: 0.10% or more and 0.16% or less, Si: 0.1% or more and 0.5% or less, Mn: 0.8% or more and 1.8% or less, P: 0.001% or more and 0.020% or less, S: 0.0050% or less, Al: 0.01% or more and 0.08% or less, Cu: 0.1% or more and 0.5% or less, Ni: 0.1% or more and 0.5% or less, Cr: 0.5% or more and 0.8% or less, Mo: 0.10% or more and 0.5% or less, Nb: 0.01% or more and 0.05% or less, Ti: 0.01% or more and 0.03% or less, N: 0.001% or more and 0.006% or less, optionally one, two, or more selected from B: 0.0005% or more and 0.0050% or less, V: 0.01% or more and 0.10% or less, Ca: 0.0005% or more and 0.0100% or less, REM: 0.0005% or more and 0.0200% or less, Zr: 0.0005% or more and 0.0300% or less, and Mg: 0.0005% or more and 0.0100% or less, and a balance of Fe and inevitable impurities, C: 0.10% or more and 0.16% or less, Si: 0.1% or more and 0.5% or less, Mn: 0.8% or more and 1.8% or less, P: 0.001% or more and 0.020% or less, S: 0.0050% or less, Al: 0.01% or more and 0.08% or less, Cu: 0.1% or more and 0.5% or less, Ni: 0.1% or more and 0.5% or less, Cr: 0.5% or more and 0.8% or less, Mo: 0.10% or more and 0.5% or less, Nb: 0.01% or more and 0.05% or less, Ti: 0.01% or more and 0.03% or less, N: 0.001% or more and 0.006% or less, optionally one, two, or more selected from B: 0.0005% or more and 0.0050% or less, V: 0.01% or more and 0.10% or less, Ca: 0.0005% or more and 0.0100% or less, REM: 0.0005% or more and 0.0200% or less, Zr: 0.0005% or more and 0.0300% or less, and Mg: 0.0005% or more and 0.0100% or less, and a balance of Fe and inevitable impurities, a microstructure at a position located at 1/2 of a thickness of the steel sheet including bainite and bainitic ferrite in a total amount of 80% or more in terms of area fraction, in which an amount of solid solution Nb is 20% or more of a total Nb mass content, a yield strength of 480 MPa or more, a tensile strength of 600 MPa or more, a yield-strength difference (ΔYS) of 100 MPa or more, where the yield-strength difference is defined as a difference in yield strength between before and after a prestrain-heat treatment, in which the steel sheet is subjected to a heat treatment at a temperature of 650°C for 60 seconds after 5% pre-straining, and a yield strength of 620 MPa or more after the prestrain-heat treatment, wherein the yield strength and the tensile strength are obtained by performing a tensile test on a JIS No. 5 tensile test piece taken from the hot-rolled steel sheet so that the tensile direction is the L-direction.