A heat pump use apparatus, comprising: a refrigerant circuit configured to circulate refrigerant; a heat medium circuit configured to allow a heat medium to flow therethrough; and a heat exchanger configured to exchange heat between the refrigerant and the heat medium, the heat medium circuit including a main passage extending through the heat exchanger, the main passage including a branching portion to which a plurality of branch passages (221, 222) branched from the main passage are connected, the branching portion being provided at a downstream end of the main passage, and a joining portion at which the plurality of branch passages are connected to each other to be joined to the main passage, the joining portion being provided at an upstream end of the main passage, the heat pump use apparatus further comprising a pressure protection device and a refrigerant leakage detection device, the pressure protection device being connected to the main passage at a connecting portion located between the heat exchanger and one of the branching portion and the joining portion, characterised by the main passage including a first interruption device configured to interrupt a flow from the heat exchanger to the connecting portion, the first interruption device being provided between the heat exchanger and the connecting portion, the main passage including a second interruption device configured to interrupt a flow from the heat exchanger to an other of the branching portion and the joining portion, the second interruption device being provided between the heat exchanger and the other of the branching portion and the joining portion, and the refrigerant leakage detection device being connected to the main passage at a portion between the first interruption device and the connecting portion, at the connecting portion, at a portion between the connecting portion and the branching portion, at a portion between the second interruption device and the heat exchanger, or at a portion between the joining portion and the second interruption device with respect to a flow direction of the heat medium. a refrigerant circuit configured to circulate refrigerant; a heat medium circuit configured to allow a heat medium to flow therethrough; and a heat exchanger configured to exchange heat between the refrigerant and the heat medium, the heat medium circuit including a main passage extending through the heat exchanger, the main passage including a branching portion to which a plurality of branch passages (221, 222) branched from the main passage are connected, the branching portion being provided at a downstream end of the main passage, and a joining portion at which the plurality of branch passages are connected to each other to be joined to the main passage, the joining portion being provided at an upstream end of the main passage, a branching portion to which a plurality of branch passages (221, 222) branched from the main passage are connected, the branching portion being provided at a downstream end of the main passage, and a joining portion at which the plurality of branch passages are connected to each other to be joined to the main passage, the joining portion being provided at an upstream end of the main passage, the heat pump use apparatus further comprising a pressure protection device and a refrigerant leakage detection device, the pressure protection device being connected to the main passage at a connecting portion located between the heat exchanger and one of the branching portion and the joining portion, characterised by the main passage including a first interruption device configured to interrupt a flow from the heat exchanger to the connecting portion, the first interruption device being provided between the heat exchanger and the connecting portion, the main passage including a second interruption device configured to interrupt a flow from the heat exchanger to an other of the branching portion and the joining portion, the second interruption device being provided between the heat exchanger and the other of the branching portion and the joining portion, and the refrigerant leakage detection device being connected to the main passage at a portion between the first interruption device and the connecting portion, at the connecting portion, at a portion between the connecting portion and the branching portion, at a portion between the second interruption device and the heat exchanger, or at a portion between the joining portion and the second interruption device with respect to a flow direction of the heat medium.