A vehicle including: a vehicle frame including a mounting frame, and a holding frame that is disposed on said mounting frame; a tank disposed between said mounting frame and said holding frame; and a tank holding device including a positioning unit that is connected to the holding frame, and that is for pushing the tank tightly against the mounting frame so as to secure the tank on the mounting frame, said positioning unit includes: a plurality of cushion members disposed between the holding frame and the tank; a plurality of threaded members connected to the holding frame, each of said threaded members being connected threadedly to one of the holding frame and a respective one of said cushion member, and being used for pushing the respective one of said cushion members tightly against the tank; characterized in that the positioning unit further includes: a plurality of nuts disposed on the holding frame, and connected threadedly and respectively to said threaded members; and a plurality of coupling members connected respectively to said threaded members and abutting respectively against said cushion members, each of said coupling members having an end formed with a threaded engaging hole that is engaged threadedly with a respective one of said threaded members, and an opposite end abutting against a respective one of said cushion members; wherein each of said cushion members has: a main portion that is made of rubber; and an abutment portion that is made of iron, that is embedded in a top end of said main portion, and that defines a receiving space receiving a respective one of said coupling members. a vehicle frame including a mounting frame, and a holding frame that is disposed on said mounting frame; a tank disposed between said mounting frame and said holding frame; and a tank holding device including a positioning unit that is connected to the holding frame, and that is for pushing the tank tightly against the mounting frame so as to secure the tank on the mounting frame, said positioning unit includes: a plurality of cushion members disposed between the holding frame and the tank; a plurality of threaded members connected to the holding frame, each of said threaded members being connected threadedly to one of the holding frame and a respective one of said cushion member, and being used for pushing the respective one of said cushion members tightly against the tank; characterized in that the positioning unit further includes: a plurality of nuts disposed on the holding frame, and connected threadedly and respectively to said threaded members; and a plurality of coupling members connected respectively to said threaded members and abutting respectively against said cushion members, each of said coupling members having an end formed with a threaded engaging hole that is engaged threadedly with a respective one of said threaded members, and an opposite end abutting against a respective one of said cushion members; wherein each of said cushion members has: a main portion that is made of rubber; and an abutment portion that is made of iron, that is embedded in a top end of said main portion, and that defines a receiving space receiving a respective one of said coupling members. a plurality of cushion members disposed between the holding frame and the tank; a plurality of threaded members connected to the holding frame, each of said threaded members being connected threadedly to one of the holding frame and a respective one of said cushion member, and being used for pushing the respective one of said cushion members tightly against the tank; characterized in that the positioning unit further includes: a plurality of nuts disposed on the holding frame, and connected threadedly and respectively to said threaded members; and a plurality of coupling members connected respectively to said threaded members and abutting respectively against said cushion members, each of said coupling members having an end formed with a threaded engaging hole that is engaged threadedly with a respective one of said threaded members, and an opposite end abutting against a respective one of said cushion members; wherein each of said cushion members has: a main portion that is made of rubber; and an abutment portion that is made of iron, that is embedded in a top end of said main portion, and that defines a receiving space receiving a respective one of said coupling members. a plurality of nuts disposed on the holding frame, and connected threadedly and respectively to said threaded members; and a plurality of coupling members connected respectively to said threaded members and abutting respectively against said cushion members, each of said coupling members having an end formed with a threaded engaging hole that is engaged threadedly with a respective one of said threaded members, and an opposite end abutting against a respective one of said cushion members; wherein each of said cushion members has: a main portion that is made of rubber; and an abutment portion that is made of iron, that is embedded in a top end of said main portion, and that defines a receiving space receiving a respective one of said coupling members. a main portion that is made of rubber; and an abutment portion that is made of iron, that is embedded in a top end of said main portion, and that defines a receiving space receiving a respective one of said coupling members.