The invention provides a two-way photosensitive thyristor chip which can be applied to an SSR with high current capacity. The two-way photosensitive thyristor chip (40) is carried with a plurality of units (42) on a surface of a semiconductor chip. Each unit (42) includes a first photosensitive thyristor portion (42a) and a second photosensitive thyristor portion (42b) which are separately formed. Each photosensitive thyristor portion (42a, 42b) has a PNPN portion which includes: an anode diffusion area (43), a substrate (41), a control electrode diffusion area (44), and a cathode diffusion area (45). The anode diffusion area (43) extends in one direction and has one conductive type of either an N type or a P type. The substrate (41) has the other conductive type of the N type or the P type. The control electrode diffusion area (44) has a conductive type corresponding to the anode diffusion area (43). The cathode diffusion area (45) is formed within the control electrode diffusion area (44) with respect to the anode diffusion area (43) and has the other conductive type of the N type or the P type.