A semiconductor storage device has a non-volatile memory, a memory controller to carry out write processing to the non-volatile memory using a write pulse, and a write pulse controller to select one of a first write mode for writing to the non-volatile memory and a second write mode for writing to the non-volatile memory with higher electric power consumption than the first write mode at higher speed than the first write mode and, when the first write mode is selected, set a pulse width of the write pulse such that the pulse width is shorter than one cycle of a clock signal used to control access to the non-volatile memory,