Abstract: The present disclosure provides a block coupler for connecting block to block for septic tank and water treatment facility. The block coupler comprises a body having a flow path therein; an inflow part having an inflow hole formed on one side of the longitudinal ends of the body so as to communicate with the flow path; an outflow part having an outflow hole formed on the other side of the longitudinal ends of the body having the inflow part so as to communicate with the flow path; and a connecting part provided at the outer end of the body having the inflow part so as to prevent the body coupled to the block from being separated.