Laser devices for silicon photonics are expected to be implemented in an integrated environment to complement CMOS devices. For this reason, quantum dot (QD) lasers with excellent thermal properties have been considered as strong candidates for Si photonics light sources. The direct growth of QD lasers on Si (001) on-axis substrates has been garnering attention owing to the possibility of monolithic integration on a CMOS-compatible wafer. In this paper, we report on the high-temperature (over 100°C) continuous-wave operation of an InAs/GaAs QD laser directly grown on on-axis Si (001) substrates through the use of only molecular beam epitaxy.