A liquid separator includes: a housing including: a first part including a first chamber a second part including a second chamber an inflow port into which a respiratory gas flows a process chamber configured to perform a trapping process to trap liquid from the respiratory gas and an outflow port from which the processed respiratory gas is discharged a filter which is disposed in the process chamber interposed between the inflow port and the outflow port, and which partitions the process chamber into the first chamber on a side of the inflow port and the second chamber on a side of the outflow port and a heating unit configured to heat at least one of the second part, the filter, and a vicinity of the filter.
