The present invention concerns an ink jet unit detachably mounted to the carriage of an ink jet recording apparatus. The ink jet unit includes an ink container for storing ink and a casing for retaining the ink container, wherein the casing and ink container are independent from each other so that the ink container can be exchangeably installed in the casing. The casing includes an ink jet recording portion, an opening for mounting the ink container thereto, a guide portion for installing the ink container into an accommodating portion through a rotary motion, a shoe portion generating a resistive feel when the ink container is inserted into the accommodating portion, and a dislocation preventive member. The shoe portion has a pressing device for maintaining fluid communication between the ink container and an ink supply tube contained in the casing.