A heat equalizing device, applied to closed heat-producing equipment. The heat-producing device comprises a closed housing (1) and at least two heat-producing elements (2) arranged in the housing (1). The heat equalizing device comprises a temperature equalizing layer (3), a graphene sheet (4), and at least one thermally conductive pad (5) or phase-change material layer. The thermally conductive pad (5) or phase-change material layer is disposed on the heat-producing elements (2), the temperature equalizing layer (3) is disposed on the thermally conductive pad (5) or phase-change material layer. The graphene sheet (4) is attached to an inner side of the housing (1) and is disposed on the temperature equalizing layer (3). A handheld ultrasonic testing apparatus comprises the heat equalizing device, a sealed housing (8), a chip (9), and a printed circuit board (10). The heat equalizing device, the chip, and the printed circuit board (10) are disposed inside the sealed housing (1). The printed circuit board (10) is provided thereon with at least two chips (9): a first chip (91) and a second chip (92). A first heat equalizing component (6) is disposed on the first chip (91), and a second heat equalizing component (7) is disposed on the second chip (92). The heat equalizing device solves the problem of excessively high local temperature on an external surface of equipment using a high-channel and high-power consumption chip, and improves user experience.L'invention concerne un dispositif d'égalisation de chaleur, appliqué à un équipement de production de chaleur fermé. Le dispositif de production de chaleur comprend un boîtier fermé (1) et au moins deux éléments de production de chaleur (2) disposés dans le boîtier (1). Le dispositif d'égalisation de chaleur comprend une couche d'égalisation de température (3), une feuille de graphène (4) et au moins un bloc thermiquement conducteur (5) ou une couche de matériau à changement de phase. Le bloc thermiquement conducteur (5)
