A battery pack, comprising: a pack housing formed with a coolant inflow port through which a coolant is introduced and a coolant discharge port through which the coolant is discharged; and a plurality of battery modules (100; 100-1, 100-2, 100-3, 100-4) disposed in a set direction inside the pack housing and including a plurality of battery cells disposed in a set direction inside a module housing, wherein the battery module (100; 100-1, 100-2, 100-3, 100-4) includes: a first coolant inlet formed at a first side of the module housing; at least one cooling flow path fluidly connected to the first coolant inlet and formed between the plurality of battery cells adjacent to each other; a first coolant outlet formed at a second side of the module housing and fluidly connected to the first coolant inlet; a second coolant inlet formed at the second side of the module housing; a second coolant outlet fluidly connected to the at least one cooling flow path and the second coolant inlet and formed at the first side of the module housing, and a baffle plate disposed on an upper portion of the plurality of battery cells and including a plurality of communication holes, wherein the coolant inflow port is fluidly connected to the first coolant inlet of the module housing, wherein the coolant discharge port is fluidly connected to the second coolant outlet of the module housing, wherein the first coolant outlet of the module housing is fluidly connected to the first coolant inlet of an adjacent battery module (100; 100-1, 100-2, 100-3, 100-4), wherein the second coolant inlet of the module housing is fluidly connected to the second coolant outlet of the adjacent battery module (100; 100-1, 100-2, 100-3, 100-4), wherein the coolant introduced into the battery pack through the coolant inflow port is sequentially supplied from the battery module closest to the coolant inflow port to the outermost battery module farthest from the coolant inflow port, and wherein as the battery modules are located farther from the coolant inflow port, a total area of the communication holes formed in the baffle plate of each battery module increases. a pack housing formed with a coolant inflow port through which a coolant is introduced and a coolant discharge port through which the coolant is discharged; and a plurality of battery modules (100; 100-1, 100-2, 100-3, 100-4) disposed in a set direction inside the pack housing and including a plurality of battery cells disposed in a set direction inside a module housing, wherein the battery module (100; 100-1, 100-2, 100-3, 100-4) includes: a first coolant inlet formed at a first side of the module housing; at least one cooling flow path fluidly connected to the first coolant inlet and formed between the plurality of battery cells adjacent to each other; a first coolant outlet formed at a second side of the module housing and fluidly connected to the first coolant inlet; a second coolant inlet formed at the second side of the module housing; a second coolant outlet fluidly connected to the at least one cooling flow path and the second coolant inlet and formed at the first side of the module housing, and a baffle plate disposed on an upper portion of the plurality of battery cells and including a plurality of communication holes, a first coolant inlet formed at a first side of the module housing; at least one cooling flow path fluidly connected to the first coolant inlet and formed between the plurality of battery cells adjacent to each other; a first coolant outlet formed at a second side of the module housing and fluidly connected to the first coolant inlet; a second coolant inlet formed at the second side of the module housing; a second coolant outlet fluidly connected to the at least one cooling flow path and the second coolant inlet and formed at the first side of the module housing, and a baffle plate disposed on an upper portion of the plurality of battery cells and including a plurality of communication holes, wherein the coolant inflow port is fluidly connected to the first coolant inlet of the module housing, wherein the coolant discharge port is fluidly connected to the second coolant outlet of the module housing, wherein the first coolant outlet of the module housing is fluidly connected to the first coolant inlet of an adjacent battery module (100; 100-1, 100-2, 100-3, 100-4), wherein the second coolant inlet of the module housing is fluidly connected to the second coolant outlet of the adjacent battery module (100; 100-1, 100-2, 100-3, 100-4), wherein the coolant introduced into the battery pack through the coolant inflow port is sequentially supplied from the battery module closest to the coolant inflow port to the outermost battery module farthest from the coolant inflow port, and wherein as the battery modules are located farther from the coolant inflow port, a total area of the communication holes formed in the baffle plate of each battery module increases.