The present disclosure provides a foldable portable metal detector including: a detection coil disk; a waterproof circuit protection compartment; a circuit component; a folding and fixing component; a fastening component; and an extension rod; the circuit component is inserted into the waterproof circuit protection compartment; the extension rod is fixedly connected to the waterproof circuit protection compartment; the circuit component is electrically coupled to the detection coil disk; the detection coil disk is provided with a bracket provided with a first through-hole and a second through-hole; the fastening component is provided with a bolt and a fixing column; the waterproof circuit protection compartment is provided with a connector provided with a connection hole; the bolt penetrates the connection hole and the first through-hole in sequence, the fixing column penetrates the second through-hole; and the waterproof circuit protection compartment is selectively rotated around the bolt.