This is a study for participants with advanced gastric or gastroesophageal junction adenocarcinoma who have had tumor progression after first-line platinum-contained therapy. The primary study hypotheses are that camrelizumab (SHR-1210) combined with apatinib prolongs overall survival (OS) for participants with tumors that show positive programmed cell death ligand 1 (PD-L1) expression.

Inclusion Criteria:

1. Histologically- or cytologically-confirmed diagnosis of gastric or gastroesophageal junction adenocarcinoma.
2. Confirmed metastatic or locally advanced, unresectable disease.
3. Progression on or after prior first-line therapy containing any platinum/fluoropyrimidine or platinum/taxane doublet.
4. Willing to provide tumor tissue for PD-L1 biomarker analysis.
5. Human epidermal growth factor receptor 2 (HER-2/neu) status known and participants with HER2/neu positive tumors show documentation of previous treatment containing trastuzumab.
6. ECOG performance status of 0 to 1.
7. Life expectancy of more than 12 weeks.
8. Signing the informed consent forms.
9. Adequate bone marrow, liver and renal function.

Exclusion Criteria:

1. Squamous cell or undifferentiated gastric cancer.
2. Known active central nervous system (CNS) metastases and/or carcinomatous meningitis.
3. Subjects with an active, known or suspected autoimmune disease. Patients with type I diabetes who are receiving a stable dose of insulin, hypothyroidism who only needs hormone replacement therapy, and skin diseases (such as eczema, vitiligo, or psoriasis) that do not require systemic treatment and do not have acute deterioration within 1 year before the screening period, are allowed.
4. Clinically significant cardiovascular and cerebrovascular diseases.
5. Subjects with high blood pressure who cannot be controlled well with antihypertensive drugs.
6. Previous digestive tract bleeding history within 3 months or evident gastrointestinal bleeding tendency.
7. Arterial / venous thrombosis events, such as cerebrovascular accidents (including transient ischemic attacks, cerebral hemorrhage, cerebral infarction), deep vein thrombosis, and pulmonary embolism, occurred within the first 6 months of randomization.
8. Subjects who have previously received anti-PD-1 / PD-L1 monoclonal antibody, anti-CTLA-4 monoclonal antibody, and VEGFR small molecule inhibitor therapy.
9. Prior systemic chemotherapy, radiotherapy and surgery within 4 weeks before the study drug administration, or any unresolved AEs > Common Terminology Criteria for Adverse Events (CTCAE) Grade 1.