Provided is a resin composition for encapsulating which is used for forming an encapsulating resin of an on-vehicle electronic control unit including a wiring substrate, a plurality of electronic components mounted on the wiring substrate, and the encapsulating resin encapsulating the electronic component, the resin composition including: a thermosetting resin; and one or more imidazole compounds, in which when a torque value is measured over time under conditions of the number of rotations of 30 rpm and a measurement temperature of 175° C. by using Labo Plastomill, a time T1 at which the torque value is less than or equal to 2 times a minimum torque value is longer than or equal to 15 seconds and shorter than or equal to 100 seconds, and the minimum torque value is greater than or equal to 0.5 N·m and less than or equal to 2.5 N·m.