PURPOSE: To provide a height adjustment mechanism for a table or the like in which an adjusted condition can be strongly maintained, and in which adjustment work can be easily performed.

CONSTITUTION: A device is provided with an installation bolt 9 rotatably installed on a caster 8, a leg support frame 7 on which the bolt 9 is to be installed, and an adjusting knob 26 rotatably disposed to be coaxial with the installation bolt 9. A position of the leg support frame 7 on the installation bolt 9 is set to be adjusted through rotation operation of the adjusting knob 26. A guide groove 10 is formed on the installation bolt 9, and a lock piece 14 having a lock member 20 to be engaged with the groove 10, and a lock piece 22 to be connected to the lock piece 14 are provided. The lock piece 14, 22 are fixed to the leg support frame 7, and the installation bolt 9 is inserted on the inner side of it. The adjusting knob 26 having a shaft part 27 which can be inserted into the lock piece 22 is provided. The shaft part 27 is provided to be threaded with the installation bolt 9, and the shaft part 7 is connected to the lock piece 22.