The invention relates to a hybrid drive device, comprising: an internal combustion engine (11a; 11b); an electrical machine (12a; 12b), which has a rotor (17a; 17b); a planetary gearbox (13a; 13b); a first cylindrical-gear partial gearbox (14a; 14b) and a second cylindrical-gear partial gearbox (15a; 15b), the first cylindrical-gear partial gearbox (14a; 14b) having a first input shaft (EW1a; EW1b) and the second cylindrical-gear partial gearbox (15a; 15b) having a second input shaft (EW2a; EW2b) arranged coaxial to the first input shaft (EW1a; EW1b); a first countershaft (V1a, V1b), which is arranged parallel to the first and the second input shafts (EW1a; EW1b; EW2a; EW2b), the internal combustion engine (11a; 11b) being connected to the planetary gearbox (13a; 13b) by means of a disconnect clutch (16a; 16b) and the electrical machine (12a; 12b) being connected directly to the planetary gearbox (13a; 13b), the first cylindrical-gear partial gearbox (14a; 14b) and the second cylindrical-gear partial gearbox (15a; 15b) being connected directly to the planetary gearbox (13a; 13b), the planetary gearbox (13a; 13b) having two planetary gear sets (P1a, P2a; P1b, P2b), a first planetary gear set (P1a; P1b) of the planetary gearbox (13a; 13b) having a ring gear (P11a; P11b), a first planet carrier (P12a; P12b), and a first sun gear (P13a; P13b); containing a common countershaft (V3a; V3b), which is present in addition to the first countershaft (V1a; V1b) and which has exactly one fixed gear (V31a; V31b) and exactly one free gear (V32a; V32b), the fixed gear (V31a; V31b) permanently meshing with a gear of the first cylindrical-gear partial gearbox (14a; 14b) and the free gear (V32a; V32b) permanently meshing with a gear of the second cylindrical-gear partial gearbox (15a; 15b), a first switching unit (25a; 25b) being provided for connecting the free gear (V32a; V32b) of the common countershaft (V3a; V3b) to the fixed gear (V31a; V31b) of the common countershaft (V3a; V3b) for conjoint rotation.