In this letter, we discuss the temperature distribution of light-illuminated Si substrates with time and the successful fabrication of high-performance, solution-processed indium-oxide thin-film transistors within an annealing time of 2 min using a high-power flash lamp under ambient conditions. The precursor films are completely converted into oxide films within 30 s using flash lamp annealing (FLA). As a result, we obtained the high performance of indium-oxide TFTs with the mobility of impressive 38.9 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> with the on/off ratio of ~104 for the irradiation time of 2 min and the mobility of 10.3 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> with the on/off ratio of ~5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> for the irradiation time of 10 s for three times, which is the highest mobility ever reported using FLA. This result will be helpful for breaking the barrier in the mass production of the next-generation semiconductors.