A vehicular door latch device includes a latch, a ratchet, a locking and unlocking mechanism, and a rotation member. The latch rotates in accordance with closing of a door while a striker provided in a vehicle body is engaged. When the door is in a fully-closed state, the ratchet holds the latch in a first posture. When the door is in a half-closed state, the ratchet holds the latch in a second posture. The mechanism is switched between an unlocked posture that can cancel interlock, and a locked posture that cannot cancel the interlock. When the latch is in the second posture, the rotation member overlaps the switching route and prohibits the posture change. When coming into contact with the rotation member overlapping the switching route, the mechanism in the unlocked posture is switched to the unlocked posture by rotation of a portion thereof in contact with the rotation member.