A heat pump mounting box for a heat pump drier or washer-drier machine, comprising: a base provided with an air suction port, a two-device mounting chamber, a compressor mounting chamber, a cooling air supplement port configured to communicate the compressor mounting chamber with the outside, and a bypass orifice configured to communicate the two-device mounting chamber with the compressor mounting chamber; an air passage guide plate mounted to the base and defining, together with the base, an air guide passage that has a drying air inlet in communication with the air suction port and a drying air outlet in communication with the two-device mounting chamber; and a cover plate mounted over the base and at least covering the two-device mounting chamber, wherein the two-device mounting chamber comprises an evaporator mounting section and a condenser mounting section communicated with each other, as well as a passage section located between the evaporator mounting section and the condenser mounting section; the air guide passage is in communication with the evaporator mounting section; and the bypass orifice is in communication with the condenser mounting section and/or the passage section, characterized in that the cooling air supplement port and the bypass orifice are disposed in two opposite side walls of the compressor mounting chamber respectively; and in that the cooling air supplement port and the bypass orifice are configured such that ambient air enters the compressor mounting chamber via the cooling air supplement port and enters the two-device mounting chamber via the bypass orifice such that the ambient air of relatively low temperature is mixed with the drying air of relatively high temperature and takes away part of heat of the condenser when passing across the condenser. a base provided with an air suction port, a two-device mounting chamber, a compressor mounting chamber, a cooling air supplement port configured to communicate the compressor mounting chamber with the outside, and a bypass orifice configured to communicate the two-device mounting chamber with the compressor mounting chamber; an air passage guide plate mounted to the base and defining, together with the base, an air guide passage that has a drying air inlet in communication with the air suction port and a drying air outlet in communication with the two-device mounting chamber; and a cover plate mounted over the base and at least covering the two-device mounting chamber, wherein the two-device mounting chamber comprises an evaporator mounting section and a condenser mounting section communicated with each other, as well as a passage section located between the evaporator mounting section and the condenser mounting section; the air guide passage is in communication with the evaporator mounting section; and the bypass orifice is in communication with the condenser mounting section and/or the passage section, characterized in that the cooling air supplement port and the bypass orifice are disposed in two opposite side walls of the compressor mounting chamber respectively; and in that the cooling air supplement port and the bypass orifice are configured such that ambient air enters the compressor mounting chamber via the cooling air supplement port and enters the two-device mounting chamber via the bypass orifice such that the ambient air of relatively low temperature is mixed with the drying air of relatively high temperature and takes away part of heat of the condenser when passing across the condenser.