The novel gaseous detector "Micro Pixel Chamber (mu-PIC)" has been developed for X-ray, gamma-ray and charged particle imaging. The mu-PIC is made based on a double-sided printing circuit board, by which a large size detector could be produced easily. The operation tests were performed successfully using a 3 cm x 3 cm mu-PIC with a 0.4 mm pitch. The gas gain and stability were measured in these tests. There is neither gain reduction nor discharge between anode and cathode at a gain of 103 for 5 days continuous operation. Also, no gain decrease was observed up to 10(7) cps(counts per second)/mm(2) intense X-ray irradiation. (C) 2002 Published by Elsevier Science B.V.