The Model SB went into production in April 1947 as a small bonnet-type truck with a payload capacity of one ton. It adopted a 995 cc 27 hp water-cooled 4-cylinder side valve engine (Type S) that had formerly been developed for the Toyopet Model SA sedan. Although the side valve technology was already dated at the time, it had the advantage of being simple in structure, light-weight, compact, and inexpensive. As the General Headquarters of the occupation forces (GHQ) restricted production of passenger cars, the Model SA sedan could not be released until October 1947, and in the meantime the Model SB truck came out in April.

In a public naming competition to celebrate the birth of Toyota's first small vehicle, "Toyopet" was chosen as the brand name. The chassis of the Model SB employed a ladder frame, rigid front and rear axles, and leaf springs. The driver's cabin and the low-floored cargo bed were separated. The headlamps placed on top of the fenders gave the SB a distinct look, although the lamps were integrated with the fenders in the next-generation model. Body variations included a universal pickup (with two auxiliary seats in an extended cab and a cargo bed integrated with the body), a 2-door light van, a 2-door station wagon, and a 4-door sedan.