NOVELTY - A biogas generator having a processing tank (11), and purification tank consisting of aerator (23), sedimentation tank (25) anaerobic filter bed tank (21), and disinfection tank which are connected to each other, is new. An organic-refuse crusher is provided to crush organic refuse, and toilet waste water supplied through branch and feed pipes.    USE - For generating biogas, in biogas electric-power-generation system (claimed) used in home and office.    ADVANTAGE - Ensures efficient decompose-treatment of organic matter. Enables to generate methane gas efficiently, without discharging methane gas to external atmosphere.    DETAILED DESCRIPTION - A biogas generator having a processing tank (11), and purification tank consisting of aerator (23), sedimentation tank (25) anaerobic filter bed tank (21), and disinfection tank which are connected to each other, is new. An organic-refuse crusher is provided to crush organic refuse, and toilet waste water supplied through branch and feed pipes. A drain pipe (29) ejects water processed by the purification tank to a water storage tank (31). The water stored in the water storage tank is collected through a feed pipe (34). Organic refuse, and waste-water supplied into a bioreactor (13) of biogas generator (2) through the branch pipes (17,18), feed pipe (16), is fermented and processed by a combined purification tank (14). Gas generated in the bioreactor is collected by gas holder (25) and the collected hydrogen is supplied to fuel cell (4) through a gas supply line (41).    An INDEPENDENT CLAIM is also included for biogas electric-power-generation system has fuel cell into which the hydrogen gas collected by a gas-treatment unit (3) is supplied, after removing foreign material in gas stored in the gas holder. A gas supply unit of biogas electric-power-generation system supplies liquefied petroleum gas (LPG) and town gas to electric power generation source through gas-treatment unit.    DESCRIPTION OF DRAWING(S) - The figure shows the block diagram of biogas electric-power-generation system. (Drawing contains non-English language text).    Biogas generator (2)    Fuel cell (4)    Bioreactor (13)    Purification tank (14)    Feed tank (16)    Branch pipes(25) gas holder (17,18)    Gas supply line (41).