A micro reactor having micro flow-guiding blocks includes a first gas flow channel, a second gas flow channel and a catalytic converter. There are several flow-guiding portions disposed on the first gas flow channel. Each flow-guiding portion has micro flow-guiding blocks, flow-impact recesses, and catalytic portions. The function of the micro flow-guiding block is to guide a flowing direction of the flow toward the catalytic portion on the flow-impact recess in order to increase a possibility of contacting and chemical reaction with the catalytic portion. So, guiding the flow direction toward the catalytic portion can increase the overall reaction efficiency. More turbulence is generated to obtain a better mixing. Plus, its structure is simple.