A signal detection circuit includes: a power terminal; a first current limitation circuit; a second current limitation circuit; a current-voltage conversion circuit; a first p-channel MOS transistor including a source, a gat, and a drain; a first n-channel MOS transistor including a drain, a gate, and a source; and a second n-channel MOS transistor in which a drain is connected to a first connection point connecting the resistor with the drain of the first n-channel MOS transistor, a gate is connected to a second connection point connecting the drain of the first p-channel MOS transistor with the current-voltage conversion circuit, and a source is grounded.