MAXI (Monitor of All-sky X-ray Image) is the first astrophysical payload for Japanese Experiment Module (JEM) to be designed for all sky X-ray monitoring. MAXI is a slit scanning camera which consists of two kinds of X-ray detectors; one is one-dimensional position sensitive proportional counters with total area of about 5000 cm2 (here we call GSC) and the other is an X-ray CCD array with total area of about 200 cm2 (here we call SSC). The GSC subtends a field of view with an angular dimension of 1° × 180°, while the SSC has a field of view of 1° × 90°. Thus, in the course of one station orbit, MAXI can scan almost all sky with a precision of 1 degree and with X-ray energy range of 0.5-30 keV. MAXI with a total weight of about 500 kg will be attached to JEM exposed facility (JEM-EF) in 2004. Furthermore, the future ASM with more sensitive detectors having a wide energy band and with better time response/resolution will follow the MAXI mission.