A refrigeration cycle apparatus comprising: a refrigerant circuit including at least a compressor, a condenser, an expansion device, and an evaporator, characterised by using an ethylene based fluorohydrocarbon or a mixture containing the ethylene based fluorohydrocarbon as refrigerant and comprising: a controller configured to control a rotation speed of the compressor and an opening degree of the expansion device; a clogging amount detection device configured to detect a clogging amount of the expansion device; and a polymerization amount estimation device configured to determine an amount of a product generated through polymerization of the refrigerant, wherein the clogging amount detection device includes a memory storing a table or a mathematical formula of Cv value showing a relationship between an opening degree of the expansion device and a theoretical Cv value, and a computation unit configured to compute an actual Cv value of the expansion device computed from an operation state of the refrigerant circuit, compute the theoretical Cv value of the expansion device in the operation state based on the table or the mathematical formula of Cv value, and compute the clogging amount of the expansion device based on the actual Cv value and theoretical Cv value, wherein the Cv value is defined by C v = M G Δ P wherein M represents a flow rate of the refrigerant flowing in the expansion device, G represents a specific gravity of the refrigerant, and ΔP represents a pressure difference between before and after the expansion device, wherein the polymerization amount estimation device includes the memory configured to store a table or a mathematical formula for estimating the production amount of the product from a polymerization occurrence temperature operation time corresponding to an operation time of the refrigerant circuit under the condition of the refrigerant being at a predetermined temperature or higher and an integrated value of the polymerization occurrence temperature operation time, and the computation unit configured to compute the integrated value of the polymerization occurrence temperature operation time and, compute the production amount of the product from the integrated value of the polymerization occurrence temperature operation time based on the table or the mathematical formula for estimating the production amount of the product. a refrigerant circuit including at least a compressor, a condenser, an expansion device, and an evaporator, characterised by using an ethylene based fluorohydrocarbon or a mixture containing the ethylene based fluorohydrocarbon as refrigerant and comprising: a controller configured to control a rotation speed of the compressor and an opening degree of the expansion device; a clogging amount detection device configured to detect a clogging amount of the expansion device; and a polymerization amount estimation device configured to determine an amount of a product generated through polymerization of the refrigerant, a controller configured to control a rotation speed of the compressor and an opening degree of the expansion device; a clogging amount detection device configured to detect a clogging amount of the expansion device; and a polymerization amount estimation device configured to determine an amount of a product generated through polymerization of the refrigerant, wherein the clogging amount detection device includes a memory storing a table or a mathematical formula of Cv value showing a relationship between an opening degree of the expansion device and a theoretical Cv value, and a computation unit configured to compute an actual Cv value of the expansion device computed from an operation state of the refrigerant circuit, compute the theoretical Cv value of the expansion device in the operation state based on the table or the mathematical formula of Cv value, and compute the clogging amount of the expansion device based on the actual Cv value and theoretical Cv value, wherein the Cv value is defined by C v = M G Δ P wherein M represents a flow rate of the refrigerant flowing in the expansion device, G represents a specific gravity of the refrigerant, and ΔP represents a pressure difference between before and after the expansion device, wherein the polymerization amount estimation device includes the memory configured to store a table or a mathematical formula for estimating the production amount of the product from a polymerization occurrence temperature operation time corresponding to an operation time of the refrigerant circuit under the condition of the refrigerant being at a predetermined temperature or higher and an integrated value of the polymerization occurrence temperature operation time, and the computation unit configured to compute the integrated value of the polymerization occurrence temperature operation time and, compute the production amount of the product from the integrated value of the polymerization occurrence temperature operation time based on the table or the mathematical formula for estimating the production amount of the product.