PURPOSE: To prevent the formation of defective product even at the initial stage of laver-making process or the finishing stage thereof, by detecting the state of laver contained in a drying chamber and controlling the flow rate, temperature or humidity of hot air supplied to the drying chamber according to the state of the laver in the chamber.

CONSTITUTION: The laver-making apparatus 30 is furnished with a switch SWa which turns on or off according to the end of laver-making process and with a switch SWb which turns on and off according to the transfer of the laver screen 21 to the laver screen conveyor. The laver-making signal is outputted from the laver-making judgement circuit 36. The counting circuit 38 counts the number of operation pulses of the switch SWb and when it coincides with the number set by the setter 40, a shift pulse is outputted from the circuit to reset the count. The content of the laver-making signal is stored in the register 42 according to the input of the shift pulse. The state of the laver stored in the drying chamber 20 is converted to the output signals P1, P2, etc., and displayed on the display 44. The flow rate and the temperature or humidity of the hot air supplied to the drying chamber are controlled according to the state of the laver in the chamber.