Tubular hollow crystals of CaCO3 were obtained by a novel synthesis process of dropping NaHCO3 solution into boiling CaCl2 solution under atmospheric pressure. Under the condition of [HCO3-]/[Ca2+] = 2, the crystals had a simple aragonite structure. Tubular hollow crystals of BaCO3 were similarly obtained by using boiling BaCl2 solution. This novel process is expected to be widely applicable to synthesis of various tubular hollow crystals.