A gas concentration detecting device consisting of catalytic burning sensors for gas concentration detection and an accompanying on-line microcomputer data collecting system was set-up to investigate axial and radial mixing characteristics of gas in adsorption bed. It could measure and record combustible gas concentration at sixteen different positions simultaneously in adsorption bed. Experiments were carried out with methane-air-5A molecular sieve in a267 mm diameter adsorption column at different gas flow rates. Methane used as adsorbate was continuously fed into the center of bed entrance section and its concentration distributions were obtained at three different levels of the column. This device can also be used to measure temperature distribution if temperature sensors are used instead of that for gas concentration measurement.