A card holder adapted for converting a micro SIM card into a standard SIM card in size and shape includes an insulating housing of a flat board shape which is in accordance with the standard SIM card in size and shape, and defines a card groove in accordance with the micro SIM card in size and shape and in accordance with the standard SIM card in contact position for receiving the micro SIM card in place. At least one elastic part is disposed in a positioning fillister of the insulating housing opened in one groove sidewall of the card groove, and elastically stretches into the card groove to resist against one end of the micro SIM card for securing the micro SIM card in the card groove. By using the card holder, the micro SIM card can be converted into the standard SIM card in size and shape.