A foldable car seat adapted to connect to vehicle seat, the foldable car seat comprising: a base frame having thereon a driver securely mounted thereon; a sliding frame operably connected to the driver and slidably attached to an inside of the base frame and having an adapter securely attached to a free end of the sliding frame to adapt to the vehicle seat so that the base frame is able to move relative to the sliding frame due to power from the motor; and a back frame foldably connected to the base frame and consisting of a pair of lower support frames foldably connected to free ends of the base frame through a first folding device and a pair of upper support frames foldably connected to free ends of the pair of lower support frames through a second folding device to allow the pair of lower support frames to fold relative to the base frame and the pair of upper support frames to fold relative to the pair of lower support frames; wherein the sliding frame has a first slider slidably attached to an inside of the base frame, a second slider oppositely located relative to the first slider and slidably attached to the inside of the base frame and a connection rod securely connected to the first slider and the second slider and having the motor securely attached thereto such that the connection rod, the first slider and the second slider are moved relative to the base frame due to the driver; a pad frame is sandwiched between the first slider and the base frame and between the second slider and the base frame and has a flange formed thereon to avoid excessive friction therebetween; the base frame includes a first side plate, a second side plate oppositely located relative to the first side plate and a connection rod sandwiched between the first side plate and the second side plate to fix locations of the first side plate and the second side plate, a bore is defined through the side face of the first side plate and of the second side plate to movably accommodate therein at least a stop which is firmly attached to a side face of the first slider and of the second slider so that extent of the movement of each of the first slider and of the second slider is limited; the back frame includes a first support frame foldably connected to distal end of the first side plate and a second support frame oppositely located relative to the first support frame and foldably connected to distal end of the second side plate, the first folding device is sandwiched between the first support frame and the distal end of the first side plate and between the second support frame and the distal end of the second side plate so that both the first support fame and the second support frame are able to fold simultaneously relative to the base frame due to the connection rod. a base frame having thereon a driver securely mounted thereon; a sliding frame operably connected to the driver and slidably attached to an inside of the base frame and having an adapter securely attached to a free end of the sliding frame to adapt to the vehicle seat so that the base frame is able to move relative to the sliding frame due to power from the motor; and a back frame foldably connected to the base frame and consisting of a pair of lower support frames foldably connected to free ends of the base frame through a first folding device and a pair of upper support frames foldably connected to free ends of the pair of lower support frames through a second folding device to allow the pair of lower support frames to fold relative to the base frame and the pair of upper support frames to fold relative to the pair of lower support frames; wherein the sliding frame has a first slider slidably attached to an inside of the base frame, a second slider oppositely located relative to the first slider and slidably attached to the inside of the base frame and a connection rod securely connected to the first slider and the second slider and having the motor securely attached thereto such that the connection rod, the first slider and the second slider are moved relative to the base frame due to the driver; a pad frame is sandwiched between the first slider and the base frame and between the second slider and the base frame and has a flange formed thereon to avoid excessive friction therebetween; the base frame includes a first side plate, a second side plate oppositely located relative to the first side plate and a connection rod sandwiched between the first side plate and the second side plate to fix locations of the first side plate and the second side plate, a bore is defined through the side face of the first side plate and of the second side plate to movably accommodate therein at least a stop which is firmly attached to a side face of the first slider and of the second slider so that extent of the movement of each of the first slider and of the second slider is limited; the back frame includes a first support frame foldably connected to distal end of the first side plate and a second support frame oppositely located relative to the first support frame and foldably connected to distal end of the second side plate, the first folding device is sandwiched between the first support frame and the distal end of the first side plate and between the second support frame and the distal end of the second side plate so that both the first support fame and the second support frame are able to fold simultaneously relative to the base frame due to the connection rod.